[SPARK-35358][BUILD] Increase maximum Java heap used for release build to avoid OOM

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

This patch proposes to increase the maximum heap memory setting for release build.

### Why are the changes needed?

When I was cutting RCs for 2.4.8, I frequently encountered OOM during building using mvn. It happens many times until I increased the heap memory setting.

I am not sure if other release managers encounter the same issue. So I propose to increase the heap memory setting and see if it looks good for others.

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

No, dev only.

### How was this patch tested?

Manually used it during cutting RCs of 2.4.8.

Closes apache#32487 from viirya/release-mvn-oom.

Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: viirya

dev/create-release/release-build.sh

@@ -162,6 +162,8 @@ git clean -d -f -x
 rm -f .gitignore
 cd ..
 
+export MAVEN_OPTS="-Xmx12g"
+
 if [[ "$1" == "package" ]]; then
   # Source and binary tarballs
   echo "Packaging release source tarballs"