gitignore Pyenv's .python-version file. (#14862)

Pyenv creates this file when you call `pyenv local`,
to set the local interpreter for the cwd.
It is just a local artifact that shouldn't be accidentally
pulled into the repo.

[ci skip-rust]

[ci skip-build-wheels]

.gitignore

@@ -31,6 +31,7 @@ __pycache__/
 .classpath
 .factorypath
 .python
+.python-version
 .pydevproject
 .pytest_cache/
 codegen/classes/
@@ -58,4 +59,4 @@ GTAGS
 /.pants
 /.pants.rc
 /.venv
-.tool-versions
+.tool-versions