[SPARK-53815][FOLLOWUP] Remove branch-0.4 from matrix too

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

This is a follow-up the following to clean up the matrix too.
- apache#367

### Why are the changes needed?

To remove it completely.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Pass the CIs.

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

No.

Closes apache#386 from dongjoon-hyun/SPARK-53815-2.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

.github/workflows/publish_snapshot_chart.yml

@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         # keep in sync with default value of workflow_dispatch input 'branch'
-        branch: ${{ fromJSON( inputs.branch || '["main", "branch-0.4"]' ) }}
+        branch: ${{ fromJSON( inputs.branch || '["main"]' ) }}
     steps:
     - name: Checkout repository
       uses: actions/checkout@v5

.github/workflows/publish_snapshot_dockerhub.yml

@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         # keep in sync with default value of workflow_dispatch input 'branch'
-        branch: ${{ fromJSON( inputs.branch || '["main", "branch-0.4"]' ) }}
+        branch: ${{ fromJSON( inputs.branch || '["main"]' ) }}
     steps:
     - name: Set up QEMU
       uses: docker/setup-qemu-action@v3