[SPARK-35388][INFRA] Allow the PR source branch to include slashes

### 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>

Author: ueshin

.github/workflows/build_and_test.yml

@@ -89,7 +89,7 @@ jobs:
       id: sync-branch
       run: |
         apache_spark_ref=`git rev-parse HEAD`
-        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF##*/}
+        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF#refs/heads/}
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' merge --no-commit --progress --squash FETCH_HEAD
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' commit -m "Merged commit"
         echo "::set-output name=APACHE_SPARK_REF::$apache_spark_ref"
@@ -186,7 +186,7 @@ jobs:
       id: sync-branch
       run: |
         apache_spark_ref=`git rev-parse HEAD`
-        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF##*/}
+        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF#refs/heads/}
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' merge --no-commit --progress --squash FETCH_HEAD
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' commit -m "Merged commit"
         echo "::set-output name=APACHE_SPARK_REF::$apache_spark_ref"
@@ -262,7 +262,7 @@ jobs:
       id: sync-branch
       run: |
         apache_spark_ref=`git rev-parse HEAD`
-        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF##*/}
+        git fetch https://github.com/$GITHUB_REPOSITORY.git ${GITHUB_REF#refs/heads/}
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' merge --no-commit --progress --squash FETCH_HEAD
         git -c user.name='Apache Spark Test Account' -c user.email='sparktestacc@gmail.com' commit -m "Merged commit"
         echo "::set-output name=APACHE_SPARK_REF::$apache_spark_ref"