Maintenance: Bump diffy from 3.4.1 to 3.4.2

Bumps [diffy](https://github.com/samg/diffy) from 3.4.1 to 3.4.2.
- [Release notes](https://github.com/samg/diffy/releases)
- [Changelog](https://github.com/samg/diffy/blob/main/CHANGELOG)
- [Commits](https://github.com/samg/diffy/commits)

Gemfile.lock

@@ -162,7 +162,7 @@ GEM
     deprecation_toolkit (2.0.0)
       activesupport (>= 5.2)
     diff-lcs (1.5.0)
-    diffy (3.4.1)
+    diffy (3.4.2)
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
     doorkeeper (5.5.4)