Bump flipper from 0.20.3 to 0.20.4 (#12934)

Bumps [flipper](https://github.com/jnunemaker/flipper) from 0.20.3 to 0.20.4.
- [Release notes](https://github.com/jnunemaker/flipper/releases)
- [Changelog](https://github.com/jnunemaker/flipper/blob/master/Changelog.md)
- [Commits](https://github.com/jnunemaker/flipper/compare/v0.20.3...v0.20.4)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

@@ -35,7 +35,7 @@ gem "emoji_regex", "~> 3.2" # A pair of Ruby regular expressions for matching Un
 gem "fastly", "~> 3.0" # Client library for the Fastly acceleration system
 gem "feedjira", "~> 3.1" # A feed fetching and parsing library
 gem "field_test", "~> 0.4" # A/B testing
-gem "flipper", "~> 0.20.3" # Feature flipping / flags for Ruby
+gem "flipper", "~> 0.20.4" # Feature flipping / flags for Ruby
 gem "flipper-active_record", "~> 0.20.3" # Store Flipper flags in ActiveRecord
 gem "flipper-ui", "~> 0.20.3"
 gem "fog-aws", "~> 3.9" # 'fog' gem to support Amazon Web Services

Gemfile.lock

@@ -307,7 +307,7 @@ GEM
       browser (>= 2.0)
       distribution
       railties (>= 5)
-    flipper (0.20.3)
+    flipper (0.20.4)
     flipper-active_record (0.20.3)
       activerecord (>= 5.0, < 7)
       flipper (~> 0.20.3)
@@ -897,7 +897,7 @@ DEPENDENCIES
   fastly (~> 3.0)
   feedjira (~> 3.1)
   field_test (~> 0.4)
-  flipper (~> 0.20.3)
+  flipper (~> 0.20.4)
   flipper-active_record (~> 0.20.3)
   flipper-ui (~> 0.20.3)
   fog-aws (~> 3.9)