chore: remove docker credentials for PRs

Author: JenniferMah

.travis.yml

@@ -18,7 +18,9 @@ before_script:
 - chmod +x ./cc-test-reporter
 - "./cc-test-reporter before-build"
 script:
-- echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
+- if [[ "$TRAVIS_BRANCH" == "main"  ||  "$TRAVIS_BRANCH" == "travis" ]] && [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
+  echo "${DOCKER_PASSWORD}" | docker login -u "${DOCKER_USERNAME}" --password-stdin
+  fi
 - make test-docker
 after_script:
 - make test-install