Update system-tests-pr.yaml

Author: franvila

.github/workflows/system-tests-pr.yaml

@@ -73,8 +73,8 @@ jobs:
         id: kafkaClient
         env:
           KAFKA_CLIENTS: ${{ steps.discover.outputs.test_clients }}
-          LABELS: ${{ github.event.pull_request.labels }}
         run: |
+          LABELS=${{ github.event.pull_request.labels.*.name }}
           KAFKA_CLIENT=$(echo "${LABELS[@]},${KAFKA_CLIENTS}" | sed 's/,/\n/g; s/\[//g; s/\]//g; s/test\/system-test\///g' | sort | uniq -d)
           KAFKA_CLIENT=$([[ -z $KAFKA_CLIENT ]] && echo 'strimzi_test_client' || echo $KAFKA_CLIENT)
           echo "kafka_client=$KAFKA_CLIENT" >> "$GITHUB_OUTPUT"