Bump aws-sigv4 from 1.1.4 to 1.2.0 (mastodon#14107)

Bumps [aws-sigv4](https://github.com/aws/aws-sdk-ruby) from 1.1.4 to 1.2.0.
- [Release notes](https://github.com/aws/aws-sdk-ruby/releases)
- [Changelog](https://github.com/aws/aws-sdk-ruby/blob/master/gems/aws-sigv4/CHANGELOG.md)
- [Commits](aws/aws-sdk-ruby@1.1.4...1.2.0)

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

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

Gemfile.lock

@@ -105,8 +105,8 @@ GEM
       aws-sdk-core (~> 3, >= 3.99.0)
       aws-sdk-kms (~> 1)
       aws-sigv4 (~> 1.1)
-    aws-sigv4 (1.1.4)
-      aws-eventstream (~> 1.0, >= 1.0.2)
+    aws-sigv4 (1.2.0)
+      aws-eventstream (~> 1, >= 1.0.2)
     bcrypt (3.1.13)
     better_errors (2.7.1)
       coderay (>= 1.0.0)