Bump octokit from 4.19.0 to 4.20.0

Bumps [octokit](https://github.com/octokit/octokit.rb) from 4.19.0 to 4.20.0.
- [Release notes](https://github.com/octokit/octokit.rb/releases)
- [Changelog](https://github.com/octokit/octokit.rb/blob/4-stable/RELEASE.md)
- [Commits](octokit/octokit.rb@v4.19.0...v4.20.0)

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

Gemfile.lock

@@ -25,9 +25,8 @@ GEM
     docile (1.3.2)
     emot (0.0.4)
       thor
-    faraday (1.1.0)
+    faraday (0.17.3)
       multipart-post (>= 1.2, < 3)
-      ruby2_keywords
     fastimage (2.2.1)
     hikidoc (0.1.0)
     jasmine (2.99.0)
@@ -49,13 +48,13 @@ GEM
     multipart-post (2.1.1)
     nokogiri (1.10.10)
       mini_portile2 (~> 2.4.0)
-    octokit (4.19.0)
+    octokit (4.20.0)
       faraday (>= 0.9)
       sawyer (~> 0.8.0, >= 0.5.3)
     phantomjs (2.1.1.0)
     pit (0.0.7)
     power_assert (1.2.0)
-    public_suffix (4.0.6)
+    public_suffix (3.1.1)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -80,7 +79,6 @@ GEM
     rspec-support (3.10.0)
     ruby-debug-ide (0.7.2)
       rake (>= 0.8.1)
-    ruby2_keywords (0.0.2)
     rubyzip (2.3.0)
     sawyer (0.8.2)
       addressable (>= 2.3.5)