Bump json from 2.1.0 to 2.3.0 (#24)

Bumps [json](https://github.com/flori/json) from 2.1.0 to 2.3.0.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.1.0...v2.3.0)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -1,16 +1,3 @@
-GIT
-  remote: git://github.com/Furtif/github-changelog-generator.git
-  revision: efa960ce1c189cd999753713fcfbfb6b7514ab45
-  specs:
-    github_changelog_generator (1.14.3)
-      activesupport
-      faraday-http-cache
-      multi_json
-      octokit (~> 4.6)
-      rainbow (>= 2.2.1)
-      rake (>= 10.0)
-      retriable (~> 3.0)
-
 GIT
   remote: https://github.com/asciidoctor/asciidoctor-epub3
   revision: ba930925a1df617312f986c7599b5162473b716f
@@ -24,11 +11,6 @@ GEM
   remote: https://rubygems.org/
   specs:
     Ascii85 (1.0.3)
-    activesupport (5.2.0)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (>= 0.7, < 2)
-      minitest (~> 5.1)
-      tzinfo (~> 1.1)
     addressable (2.5.2)
       public_suffix (>= 2.0.2, < 4.0)
     afm (0.2.2)
@@ -43,38 +25,23 @@ GEM
       safe_yaml (~> 1.0.4)
       thread_safe (~> 0.3.6)
       treetop (= 1.5.3)
-    asciidoctor-pdf-cjk (0.1.3)
-      asciidoctor-pdf (~> 1.5.0.alpha.8)
-    asciidoctor-pdf-cjk-kai_gen_gothic (0.1.1)
-      asciidoctor-pdf-cjk (~> 0.1.2)
     awesome_print (1.8.0)
     coderay (1.1.2)
-    concurrent-ruby (1.0.5)
     css_parser (1.6.0)
       addressable
-    epubcheck-ruby (4.0.2.1)
-    faraday (0.15.0)
-      multipart-post (>= 1.2, < 3)
-    faraday-http-cache (2.0.0)
-      faraday (~> 0.8)
+    epubcheck (3.0.1)
     gepub (0.6.9.2)
       nokogiri (~> 1.6.1)
       rubyzip (>= 1.1.1)
     hashery (2.1.2)
-    i18n (1.0.1)
-      concurrent-ruby (~> 1.0)
-    json (2.1.0)
+    json (2.3.0)
     kindlegen (3.0.3)
       rake
       rubyzip
     mini_portile2 (2.1.0)
-    minitest (5.11.3)
     multi_json (1.13.1)
-    multipart-post (2.0.0)
     nokogiri (1.6.8.1)
       mini_portile2 (~> 2.1.0)
-    octokit (4.8.0)
-      sawyer (~> 0.8.0, >= 0.5.3)
     pdf-core (0.7.0)
     pdf-reader (2.1.0)
       Ascii85 (~> 1.0.0)
@@ -99,21 +66,14 @@ GEM
     public_suffix (3.0.2)
     pygments.rb (1.2.1)
       multi_json (>= 1.0.0)
-    rainbow (3.0.0)
     rake (12.3.1)
-    retriable (3.1.1)
     ruby-rc4 (0.1.5)
     rubyzip (1.2.1)
     safe_yaml (1.0.4)
-    sawyer (0.8.1)
-      addressable (>= 2.3.5, < 2.6)
-      faraday (~> 0.8, < 1.0)
     thread_safe (0.3.6)
     treetop (1.5.3)
       polyglot (~> 0.3)
     ttfunk (1.5.1)
-    tzinfo (1.2.5)
-      thread_safe (~> 0.1)
 
 PLATFORMS
   ruby
@@ -122,15 +82,11 @@ DEPENDENCIES
   asciidoctor (= 1.5.6.1)
   asciidoctor-epub3!
   asciidoctor-pdf (= 1.5.0.alpha.16)
-  asciidoctor-pdf-cjk (~> 0.1.3)
-  asciidoctor-pdf-cjk-kai_gen_gothic (~> 0.1.1)
   awesome_print
   coderay
-  epubcheck-ruby
-  github_changelog_generator!
+  epubcheck
   json
   kindlegen
-  octokit
   pygments.rb
   rake
   thread_safe