add instruction to push new branch

Added instructions to push the new branch after cherry-picking commits.

Author: kevinjqliu

mkdocs/docs/how-to-release.md

@@ -96,6 +96,9 @@ git checkout -b pyiceberg-0.8.x pyiceberg-0.8.0
 
 # Cherry-pick commits for the upcoming patch release
 git cherry-pick <commit>
+
+# Push the new branch
+git push git@github.com:apache/iceberg-python.git pyiceberg-0.8.x
 ```
 
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