### What changes were proposed in this pull request?
This PR allows the PR source branch to include slashes.
### Why are the changes needed?
There are PRs whose source branches include slashes, like `issues/SPARK-35119/gha` here or #32523.
Before the fix, the PR build fails in `Sync the current branch with the latest in Apache Spark` phase.
For example, at #32523, the source branch is `issues/SPARK-35382/nested_higher_order_functions`:
```
...
fatal: couldn't find remote ref nested_higher_order_functions
Error: Process completed with exit code 128.
```
(https://github.com/ueshin/apache-spark/runs/2569356241)
### Does this PR introduce _any_ user-facing change?
No, this is a dev-only change.
### How was this patch tested?
This PR source branch includes slashes and #32525 doesn't.
Closes#32524 from ueshin/issues/SPARK-35119/gha.
Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
c0b52da89e