[ci] fix pypi publishing trigger (#1444)

## Which issue does this PR close?



## What changes are included in this PR?
Follow up to #1379. This PR changes the pypi publishing step to trigger
on previous workflow's successful run

Also see
#1325 (comment)


## Are these changes tested?

yes, tested the new logic
```
if: ${{ !contains(github.event.workflow_run.head_branch, '-') || github.event_name == 'workflow_dispatch' }}
```
by pushing a new tag to my fork and checking the github workflow run

-
[publish](https://github.com/kevinjqliu/iceberg-rust/actions/runs/15658709460/job/44113281419)
-
[pypi](https://github.com/kevinjqliu/iceberg-rust/actions/runs/15658721165/job/44113329600),
the job triggered

Author: kevinjqliu

.github/workflows/release_python.yml

@@ -100,7 +100,8 @@ jobs:
     needs: [sdist, wheels]
     runs-on: ubuntu-latest
     # Only publish to PyPi if the tag is not a pre-release OR if manually triggered
-    if: ${{ (startsWith(github.ref, 'refs/tags/') && !contains(github.ref, '-')) || github.event_name == 'workflow_dispatch' }}
+    # Note, `workflow_run.head_branch` does not contain `refs/tags/` prefix, just the tag name, i.e. `v0.4.0` or `v0.4.0-rc.1`
+    if: ${{ !contains(github.event.workflow_run.head_branch, '-') || github.event_name == 'workflow_dispatch' }}
 
     environment:
       name: pypi