[MINOR] add .venv into .gitignore

### What changes were proposed in this pull request?

add .venv into .gitignore

### Why are the changes needed?
potential virtual environment for python or doc builds to put a heavy load on git

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?

existing tests

### Was this patch authored or co-authored using generative AI tooling?

no

Closes #53836 from yaooqinn/minor2.

Lead-authored-by: Kent Yao <kentyao@microsoft.com>
Co-authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

Author: yaooqinn

.gitignore

@@ -18,6 +18,7 @@
 .ensime
 .ensime_cache/
 .ensime_lucene
+.venv
 .generated-mima*
 .idea/
 .idea_modules/