mypy: Update the build instruction to exclude broken Python 3.13 builds

pypi/projects/mypy/build.md

@@ -8,7 +8,7 @@ $ cd mypy_mypyc-wheels
 $ git checkout ${RELEASE_TAG}
 $ git clone https://github.com/python/mypy --recurse-submodules
 $ git -C mypy checkout $(cat mypy_commit)
-$ pipx run cibuildwheel --config=cibuildwheel.toml --platform=linux --archs=aarch64 mypy
+$ CIBW_BUILD="cp310-* cp311-* cp312-*" pipx run cibuildwheel --config=cibuildwheel.toml --platform=linux --archs=aarch64 mypy
 ```
 
 The build takes about *two hours* at an aarch64 Linux VM (with 16 GB RAM allocated) running on an Apple Silicon (M1, arm64) machine.