Add workflow_dispatch to python.yml

[traversaro]

To easily trigger the rebuild, related to #437 .

[traversaro]

The Python CI/CD is still failing:

* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - cmake-build-extension>=0.3.2
  - cmake>=3.16
  - ninja
  - setuptools>=45
  - setuptools_scm[toml]>=6.0
  - wheel
* Getting build dependencies for sdist...
running egg_info
creating ycm_cmake_modules.egg-info
writing ycm_cmake_modules.egg-info/PKG-INFO
writing dependency_links to ycm_cmake_modules.egg-info/dependency_links.txt
writing top-level names to ycm_cmake_modules.egg-info/top_level.txt
writing manifest file 'ycm_cmake_modules.egg-info/SOURCES.txt'
writing manifest file 'ycm_cmake_modules.egg-info/SOURCES.txt'
/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/config/expand.py:124: SetuptoolsWarning: File '/home/runner/work/ycm-cmake-modules/ycm-cmake-modules/tools/pip/README.md; charset=UTF-8' cannot be found
  return '\n'.join(
/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/config/expand.py:124: SetuptoolsWarning: File '/home/runner/work/ycm-cmake-modules/ycm-cmake-modules/tools/pip/README.md; charset=UTF-8' cannot be found
  return '\n'.join(
* Building sdist...
running sdist
running egg_info
writing ycm_cmake_modules.egg-info/PKG-INFO
writing dependency_links to ycm_cmake_modules.egg-info/dependency_links.txt
writing top-level names to ycm_cmake_modules.egg-info/top_level.txt
writing manifest file 'ycm_cmake_modules.egg-info/SOURCES.txt'
running check
/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/config/expand.py:124: SetuptoolsWarning: File '/home/runner/work/ycm-cmake-modules/ycm-cmake-modules/tools/pip/README.md; charset=UTF-8' cannot be found
  return '\n'.join(
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 373, in <module>
    main()
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 357, in main
    json_out["return_val"] = hook(**hook_input["kwargs"])
  File "/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 326, in build_sdist
    return backend.build_sdist(sdist_directory, config_settings)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/build_meta.py", line 432, in build_sdist
    return self._build_with_temp_dir(
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/build_meta.py", line 403, in _build_with_temp_dir
    self.run_setup()
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/build_meta.py", line 318, in run_setup
    exec(code, locals())
  File "<string>", line 20, in <module>
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/__init__.py", line 117, in setup
    return distutils.core.setup(**attrs)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/_distutils/core.py", line 184, in setup
    return run_commands(dist)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/_distutils/core.py", line 200, in run_commands
    dist.run_commands()
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/_distutils/dist.py", line 954, in run_commands
    self.run_command(cmd)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/dist.py", line 950, in run_command
    super().run_command(command)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/_distutils/dist.py", line 973, in run_command
    cmd_obj.run()
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/command/sdist.py", line 68, in run
    self.make_distribution()
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/command/sdist.py", line 84, in make_distribution
    orig.sdist.make_distribution(self)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/setuptools/_distutils/command/sdist.py", line 501, in make_distribution
    self.make_release_tree(base_dir, self.filelist.files)
  File "/tmp/build-env-lfp6n3r0/lib/python3.8/site-packages/cmake_build_extension/sdist_command.py", line 36, in make_release_tree
    setuptools_scm.integration.Configuration.from_file(
AttributeError: module 'setuptools_scm.integration' has no attribute 'Configuration'

ERROR Backend subprocess exited when trying to invoke build_sdist
Error: Process completed with exit code 1.