issue template: dart of flutter (#130)

Author: bruno-garcia

.github/ISSUE_TEMPLATE/FEATURE_REQUEST.md

@@ -1,8 +1,6 @@
 ---
 name: Request a new feature
-about: New feature for the sentry_flutter package.
+about: New feature for the sentry or sentry_flutter packages.
 ---
 
-<!--  Continue to request a feature for the **Sentry Flutter SDK**.
-Feature requests for the core sentry package, please use the the sentry-dart issue tracker:
-http://github.com/getsentry/sentry-dart/issues  -->
+<!-- Please clarify if this feature is for Flutter or just Dart (i.e AngularDart, CLI, Server) -->