Bump puma from 3.3.0 to 5.6.7 in /docs-book/final_app

Bumps [puma](https://github.com/puma/puma) from 3.3.0 to 5.6.7.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.3.0...v5.6.7)

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

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

Author: dependabot[bot]

docs-book/final_app/Gemfile.lock

@@ -12,12 +12,20 @@ GEM
     faraday (0.9.2)
       multipart-post (>= 1.2, < 3)
     libv8 (3.16.14.7)
-    mimemagic (0.3.0)
+    mimemagic (0.4.3)
+      nokogiri (~> 1)
+      rake
+    mini_portile2 (2.4.0)
     multi_json (1.11.2)
     multipart-post (2.0.0)
-    puma (3.3.0)
+    nio4r (2.5.2)
+    nokogiri (1.10.10)
+      mini_portile2 (~> 2.4.0)
+    puma (5.6.7)
+      nio4r (~> 2.0)
     rack (1.5.2)
     rack-rewrite (1.5.0)
+    rake (13.0.6)
     ref (1.0.5)
     sendgrid-ruby (1.1.5)
       faraday (~> 0.9)