Bump redis-namespace from 1.8.0 to 1.8.1 (#15676)

Bumps [redis-namespace](https://github.com/resque/redis-namespace) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/resque/redis-namespace/releases)
- [Changelog](https://github.com/resque/redis-namespace/blob/master/CHANGELOG.md)
- [Commits](https://github.com/resque/redis-namespace/compare/v1.8.0...v1.8.1

)

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

Gemfile.lock

@@ -495,7 +495,7 @@ GEM
     redis-activesupport (5.2.0)
       activesupport (>= 3, < 7)
       redis-store (>= 1.3, < 2)
-    redis-namespace (1.8.0)
+    redis-namespace (1.8.1)
       redis (>= 3.0.4)
     redis-rack (2.1.3)
       rack (>= 2.0.8, < 3)