Fix label of good first issue template (ros-controls#1438)

Author: christophfroehlich

.github/ISSUE_TEMPLATE/good-first-issue.md

@@ -2,7 +2,7 @@
 name: Good first issue
 about: Create an issue to welcome a new contributor into the community.
 title: ''
-labels: good-first-issue
+labels: ["good first issue"]
 assignees: ''
 
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