fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-PUMA-6146928

Gemfile

@@ -9,7 +9,7 @@ ruby '3.0.0'
 gem 'rails', '~> 6.1.3.2'
 
 # Use Puma as the app server
-gem 'puma', '~> 4.3.11'
+gem 'puma', '~> 5.6.8'
 
 # Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
 gem 'sass-rails', '~> 6.0.0'

Gemfile.lock

@@ -172,7 +172,7 @@ GEM
     multi_json (1.15.0)
     multipart-post (2.1.1)
     ngrok-tunnel (2.1.1)
-    nio4r (2.5.8)
+    nio4r (2.7.0)
     nokogiri (1.11.7)
       mini_portile2 (~> 2.5.0)
       racc (~> 1.4)
@@ -188,7 +188,7 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (4.0.6)
-    puma (4.3.11)
+    puma (5.6.8)
       nio4r (~> 2.0)
     puma-ngrok-tunnel (1.2.0)
       ngrok-tunnel (~> 2.1, >= 2.1.1)
@@ -344,7 +344,7 @@ DEPENDENCIES
   parallel
   pg
   pry-rails
-  puma (~> 4.3.11)
+  puma (~> 5.6.8)
   puma-ngrok-tunnel (>= 1.2.0)
   rack-cors
   rails (~> 6.1.3.2)
@@ -370,4 +370,4 @@ RUBY VERSION
    ruby 3.0.0p0
 
 BUNDLED WITH
-   2.2.24
+   2.2.3