Bump fastimage from 2.1.4 to 2.1.5 (#9395)

Bumps [fastimage](https://github.com/sdsykes/fastimage) from 2.1.4 to 2.1.5.
- [Release notes](https://github.com/sdsykes/fastimage/releases)
- [Commits](https://github.com/sdsykes/fastimage/compare/v2.1.4...v2.1.5)

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

Gemfile.lock

@@ -210,7 +210,7 @@ GEM
     faraday (0.15.0)
       multipart-post (>= 1.2, < 3)
     fast_blank (1.0.0)
-    fastimage (2.1.4)
+    fastimage (2.1.5)
     ffi (1.9.25)
     fog-core (2.1.0)
       builder