Remove tests for pypy3.8

Pypy3.8 is prone to segfaults running pytest.  This has been fixed in
3.9 and 3.10 (https://pypy.org/posts/2024/03/fixing-bug-incremental-gc.html)
but 3.8 is no longer supported and has not been fixed.

.github/workflows/ci-tests.yml

@@ -21,27 +21,20 @@ jobs:
                     - "3.10"
                     - "3.11"
                     - "3.12"
-                    - "pypy-3.8"
                     - "pypy-3.9"
                     - "pypy-3.10"
                 os:
                     - "ubuntu-latest"
                     - "windows-latest"
                     - "macos-latest"
                 include:
-                  - py: "pypy-3.8"
-                    toxenv: "pypy38"
                   - py: "pypy-3.9"
                     toxenv: "pypy39"
                   - py: "pypy-3.10"
                     toxenv: "pypy310"
                 exclude:
                     # Don't run all PyPy versions except latest on
                     # Windows/macOS. They are expensive to run.
-                    - os: "windows-latest"
-                      py: "pypy-3.8"
-                    - os: "macos-latest"
-                      py: "pypy-3.8"
                     - os: "windows-latest"
                       py: "pypy-3.9"
                     - os: "macos-latest"

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 envlist =
     lint,
-    py38,py39,py310,py311,py312,pypy38,pypy39,pypy310,
+    py38,py39,py310,py311,py312,pypy39,pypy310,
     coverage,
     docs,
 isolated_build = True
@@ -10,7 +10,6 @@ isolated_build = True
 commands =
     python --version
     python -m pytest \
-    pypy38: --no-cov \
     pypy39: --no-cov \
     pypy310: --no-cov \
         {posargs:}