chore(travis): actually skip build on deployment job when from Pull Request

Author: Narretz

scripts/travis/build.sh

@@ -47,7 +47,7 @@ case "$JOB" in
     ;;
   "deploy")
     # we never deploy on Pull requests, so it's safe to skip the build here
-    if [[ $TRAVIS_PULL_REQUEST != 'false' ]]; then
+    if [[ "$TRAVIS_PULL_REQUEST" == "false" ]]; then
       grunt package
       grunt compress:firebaseCodeDeploy
     else