Bump yard from 0.9.19 to 0.9.20

Bumps [yard](https://github.com/lsegal/yard) from 0.9.19 to 0.9.20.
- [Release notes](https://github.com/lsegal/yard/releases)
- [Changelog](https://github.com/lsegal/yard/blob/master/CHANGELOG.md)
- [Commits](lsegal/yard@v0.9.19...v0.9.20)

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

Author: dependabot[bot]

Gemfile.lock

@@ -240,7 +240,7 @@ GEM
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
     unicode-display_width (1.6.0)
-    yard (0.9.19)
+    yard (0.9.20)
     yard-coderay (0.1.0)
       coderay
       yard