Fix wrong target branch in the iOS 4.x pipeline (#96)

Author: davidmartos96

.github/workflows/OCV-PR-4.x-iOS.yaml

@@ -29,7 +29,7 @@ jobs:
         timeout-minutes: 60
         run: |
           if [[ "${{ github.event.repository.name }}" == "ci-gha-workflow" || "${{ github.event_name }}" == "schedule" ]]; then
-            echo "TARGET_BRANCH_NAME=3.4" >> $GITHUB_ENV
+            echo "TARGET_BRANCH_NAME=4.x" >> $GITHUB_ENV
           else
             echo "BUILD_PRECOMMIT=1" >> $GITHUB_ENV
           fi