Use flutter pub get instead of pub get

Author: DavidMina96

.circleci/config.yml

@@ -6,7 +6,7 @@ jobs:
     steps:
       - checkout
       - run: flutter doctor
-      - run: pub get
+      - run: flutter pub get
       - run: flutter test
       - run: dartanalyzer --options analysis_options.yaml --fatal-warnings lib
       - run: flutter pub publish --dry-run