chore(project): do not link upstream PRs against master

tasks/wiredeps

@@ -2,7 +2,12 @@
 
 FEATURE_BRANCH=
 
-if [ "$TRAVIS_TAG" == "" ]; then
+# https://docs.travis-ci.com/user/environment-variables
+
+if [ "$TRAVIS_TAG" <> "" ] || [ "$TRAVIS_BRANCH" == "master" ]; then
+  exit 0;
+fi
+
 if [ "$TRAVIS_PULL_REQUEST_BRANCH" != "" ]; then
   FEATURE_BRANCH="$TRAVIS_PULL_REQUEST_BRANCH";
 else
@@ -18,4 +23,3 @@ if [ "$TRAVIS_TAG" == "" ]; then
 
   npm install "diagram-js@bpmn-io/diagram-js#develop";
 fi
-fi