message: Fix link "bugs" in CONTRIBUTING.md
  The link used to point to [GitHub label "bugs"](https://github.com/backstage/backstage/labels/bugs) which doesn't exist. The [correct label is "bug"](https://github.com/backstage/backstage/labels/bug).
diff: @@ -16,7 +16,7 @@ No one likes bugs. Report bugs as an issue [here](https://github.com/backstage/b
  ### Fix bugs or build new features
  -Look through the GitHub issues for [bugs](https://github.com/backstage/backstage/labels/bugs), [good first issues](https://github.com/backstage/backstage/labels/good%20first%20issue) or [help wanted](https://github.com/backstage/backstage/labels/help%20wanted).
  +Look through the GitHub issues for [bugs](https://github.com/backstage/backstage/labels/bug), [good first issues](https://github.com/backstage/backstage/labels/good%20first%20issue) or [help wanted](https://github.com/backstage/backstage/labels/help%20wanted).
  ### Build a plugin
  