Bump puma from 4.3.8 to 4.3.12 (#35)

Bumps [puma](https://github.com/puma/puma) from 4.3.8 to 4.3.12.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v4.3.8...v4.3.12)

---
updated-dependencies:
- dependency-name: puma
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

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

Gemfile.lock

@@ -140,13 +140,13 @@ GEM
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
     mysql2 (0.5.3)
-    nio4r (2.5.7)
+    nio4r (2.5.8)
     nokogiri (1.12.5)
       mini_portile2 (~> 2.6.1)
       racc (~> 1.4)
     popper_js (1.14.5)
     public_suffix (4.0.6)
-    puma (4.3.8)
+    puma (4.3.12)
       nio4r (~> 2.0)
     racc (1.5.2)
     rack (2.2.3.1)