Bump phony from 2.20.15 to 2.21.1

Bumps [phony](https://github.com/floere/phony) from 2.20.15 to 2.21.1.
- [Changelog](https://github.com/floere/phony/blob/master/history.textile)
- [Commits](floere/phony@v2.20.15...v2.21.1)

---
updated-dependencies:
- dependency-name: phony
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -76,7 +76,7 @@ GEM
     parser (3.2.2.4)
       ast (~> 2.4.1)
       racc
-    phony (2.20.15)
+    phony (2.21.1)
     psych (5.1.2)
       stringio
     racc (1.8.1)