[SPARK-52421][INFRA][FOLLOW-UP] Fix the link for KEYS

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

This PR addresses a comment in #51122 (comment)

### Why are the changes needed?

To use the recommended link

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

No, dev-only.

### How was this patch tested?

N/A

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

No.

Closes #51147 from HyukjinKwon/SPARK-52421-followup.

Authored-by: Hyukjin Kwon <[email protected]>
Signed-off-by: Hyukjin Kwon <[email protected]>

Author: HyukjinKwon

dev/create-release/release-build.sh

@@ -665,7 +665,7 @@ EOF
       echo "https://dist.apache.org/repos/dist/dev/spark/${GIT_REF}-bin/"
       echo
       echo "Signatures used for Spark RCs can be found in this file:"
-      echo "https://dist.apache.org/repos/dist/dev/spark/KEYS"
+      echo "https://downloads.apache.org/spark/KEYS"
       echo
       echo "The staging repository for this release can be found at:"
       echo "https://repository.apache.org/content/repositories/${staged_repo_id}/"

dev/create-release/vote.tmpl

@@ -15,7 +15,7 @@ The release files, including signatures, digests, etc. can be found at:
 https://dist.apache.org/repos/dist/dev/spark/{tag}-bin/
 
 Signatures used for Spark RCs can be found in this file:
-https://dist.apache.org/repos/dist/dev/spark/KEYS
+https://downloads.apache.org/spark/KEYS
 
 The staging repository for this release can be found at:
 https://repository.apache.org/content/repositories/orgapachespark-{repo_id}/