build(deps): bump puma from 5.6.4 to 5.6.9

Bumps [puma](https://github.com/puma/puma) from 5.6.4 to 5.6.9.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v5.6.4...v5.6.9)

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

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

Gemfile

@@ -24,7 +24,7 @@ gem 'jquery-rails', '~> 4.4', '>= 4.4.0'
 gem 'loofah', '>= 2.4.0'
 gem 'mysql2', '~> 0.5'
 gem 'pkg-config', '~> 1.1'
-gem 'puma', '~> 5.5' # app server
+gem 'puma', '~> 5.6' # app server
 gem 'rails', '~> 5.2'
 gem 'rails_autolink'
 gem 'rollbar' # Error reporting tool

Gemfile.lock

@@ -275,7 +275,7 @@ GEM
     net-scp (3.0.0)
       net-ssh (>= 2.6.5, < 7.0.0)
     net-ssh (6.1.0)
-    nio4r (2.5.8)
+    nio4r (2.7.3)
     nokogiri (1.12.5)
       mini_portile2 (~> 2.6.1)
       racc (~> 1.4)
@@ -294,7 +294,7 @@ GEM
     popper_js (1.16.0)
     powerpack (0.1.3)
     public_suffix (4.0.7)
-    puma (5.6.4)
+    puma (5.6.9)
       nio4r (~> 2.0)
     racc (1.6.0)
     rack (2.2.3)
@@ -504,7 +504,7 @@ DEPENDENCIES
   loofah (>= 2.4.0)
   mysql2 (~> 0.5)
   pkg-config (~> 1.1)
-  puma (~> 5.5)
+  puma (~> 5.6)
   rails (~> 5.2)
   rails-controller-testing (>= 1.0.4)
   rails_autolink