ci: Run Linkage Checker for all relevant modules

Author: lqiu96

.kokoro/nightly/downstream-protobuf-binary-compatibility.sh

@@ -49,7 +49,7 @@ for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
 
   # Match all artifacts that start with google-cloud (rules out proto and grpc modules)
   # Exclude any matches to BOM artifacts or emulators
-  ARTIFACT_LIST=$(cat "versions.txt" | grep "^google-cloud" | grep -v "bom|emulator" | tr '\n' ',')
+  ARTIFACT_LIST=$(cat "versions.txt" | grep "^google-cloud" | grep -vE "(bom|emulator)" | tr '\n' ',')
   ARTIFACT_LIST=${ARTIFACT_LIST%,}
 
   echo "Found artifacts ${ARTIFACT_LIST}"