ci: release, ignore snapshot versions

Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

.github/workflows/release.yaml

@@ -49,6 +49,7 @@ jobs:
           git config user.email "oss@extism.org"
 
       - name: Set the version
+        if: ${{ ! endsWith(github.event.inputs.release-version, '-SNAPSHOT') }}
         run: |
           mvn --batch-mode --no-transfer-progress versions:set -DgenerateBackupPoms=false -DnewVersion=${{ github.event.inputs.release-version }}
           git add .