build: fail if PR is made to non-main branch (#1681)

Author: pynappo

.github/workflows/protect_release_branches.yml

@@ -21,7 +21,7 @@ jobs:
         run: |
           target=${{ github.base_ref }}
           echo "Target is: $target"
-          if [[ $target  == "v2.x" ]]; then
+          if [[ $target != "main" ]]; then
             echo "PRs must target main"
             exit 1
           else