[cd build] Update Python version requirements

According to what GitHub runners support

Author: bact

nlpo3-python/README.md

@@ -86,11 +86,11 @@ segment("สวัสดีครับ", dict_name="dict_name", safe=True)
 ### Requirements
 
 - [Rust 2018 Edition](https://www.rust-lang.org/tools/install)
-- Python 3.6 or newer
+- Python 3.9 or newer
 - Python Development Headers
   - Ubuntu: `sudo apt-get install python3-dev`
   - macOS: No action needed
-- [PyO3](https://github.com/PyO3/pyo3) - already included in Cargo.toml
+- [PyO3](https://github.com/PyO3/pyo3) - already included in `Cargo.toml`
 - [setuptools-rust](https://github.com/PyO3/setuptools-rust)
 
 ### Steps

nlpo3-python/pyproject.toml

@@ -7,7 +7,7 @@ name = "nlpo3"
 version = "1.3.1-dev"
 description = "Python binding for nlpO3 Thai language processing library in Rust"
 readme = "README.md"
-requires-python = ">=3.6"
+requires-python = ">=3.9"
 license = { text = "Apache-2.0" }
 keywords = ["thai", "tokenizer", "nlp", "word-segmentation", "pythainlp"]
 authors = [
@@ -38,7 +38,7 @@ homepage = "https://github.com/PyThaiNLP/nlpo3/"
 repository = "https://github.com/PyThaiNLP/nlpo3/"
 
 [tool.poetry.dependencies]
-python = "^3.6"
+python = "^3.9"
 
 [tool.poetry.dev-dependencies]
 pytest = "*"