[SPARK-31691][INFRA] release-build.sh should ignore a fallback output…

… from `build/mvn`

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

This PR adds `i` option to ignore additional `build/mvn` output which is irrelevant to version string.

### Why are the changes needed?

SPARK-28963 added additional output message, `Falling back to archive.apache.org to download Maven` in build/mvn. This breaks `dev/create-release/release-build.sh` and currently Spark Packaging Jenkins job is hitting this issue consistently and broken.
- https://amplab.cs.berkeley.edu/jenkins/view/Spark%20Packaging/job/spark-master-maven-snapshots/2912/console

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

No.

### How was this patch tested?

This happens only when the mirror fails. So, this is verified manually hiject the script. It works like the following.
```
$ echo 'Falling back to archive.apache.org to download Maven' > out
$ build/mvn help:evaluate -Dexpression=project.version >> out
Using `mvn` from path: /Users/dongjoon/PRS/SPARK_RELEASE_2/build/apache-maven-3.6.3/bin/mvn
$ cat out | grep -v INFO | grep -v WARNING | grep -v Download
Falling back to archive.apache.org to download Maven
3.1.0-SNAPSHOT
$ cat out | grep -v INFO | grep -v WARNING | grep -vi Download
3.1.0-SNAPSHOT
```

Closes #28514 from dongjoon-hyun/SPARK_RELEASE_2.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

dev/create-release/release-build.sh

@@ -103,7 +103,7 @@ if [ -z "$SPARK_VERSION" ]; then
   # Run $MVN in a separate command so that 'set -e' does the right thing.
   TMP=$(mktemp)
   $MVN help:evaluate -Dexpression=project.version > $TMP
-  SPARK_VERSION=$(cat $TMP | grep -v INFO | grep -v WARNING | grep -v Download)
+  SPARK_VERSION=$(cat $TMP | grep -v INFO | grep -v WARNING | grep -vi Download)
   rm $TMP
 fi