Bump octokit version to work around Faraday issue

Without this, we get failing builds with:

```
NameError: uninitialized constant Faraday::Error::ClientError
Did you mean?  Faraday::ClientError
```

This is documented in octokit/octokit.rb#1154.

Gemfile.lock

@@ -53,7 +53,8 @@ GEM
     jaro_winkler (1.5.4)
     minitest (5.11.3)
     multipart-post (2.1.1)
-    octokit (4.13.0)
+    octokit (4.22.0)
+      faraday (>= 0.9)
       sawyer (~> 0.8.0, >= 0.5.3)
     parallel (1.19.1)
     parser (2.7.1.2)