Bump mini_magick from 4.12.0 to 4.13.1

Bumps [mini_magick](https://github.com/minimagick/minimagick) from 4.12.0 to 4.13.1.
- [Release notes](https://github.com/minimagick/minimagick/releases)
- [Commits](https://github.com/minimagick/minimagick/compare/v4.12.0...v4.13.1)

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

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

Gemfile.lock

@@ -269,7 +269,7 @@ GEM
     mimemagic (0.4.3)
       nokogiri (~> 1)
       rake
-    mini_magick (4.12.0)
+    mini_magick (4.13.1)
     mini_mime (1.1.5)
     mini_portile2 (2.8.7)
     minitest (5.23.1)