fix typo

.travis/docker.sh

@@ -7,7 +7,7 @@ CURL_URL="https://registry.hub.docker.com/u/rocketchat/rocket.chat/trigger/$PUSH
 if ["$TRAVIS_TAG" ]; then
   CURL_DATA='{"source_type":"Tag","source_name":"'"$TRAVIS_TAG"'","docker_tag":"'"$TRAVIS_TAG"'"}';
 else
-  if ["$TRAVIS_BRANCH" ="master" ]; then
+  if [ "$TRAVIS_BRANCH" == "master" ]; then
     CURL_DATA='{"source_type":"Branch","source_name":"master","docker_tag":"latest"}';
   else
     CURL_DATA='{"source_type":"Branch","source_name":"'"$TRAVIS_BRANCH"'","docker_tag":"'"$TRAVIS_BRANCH"'"}';