Bump turbolinks from 5.1.1 to 5.2.1

Bumps turbolinks from 5.1.1 to 5.2.1.

Commits

• 4fffc80 turbolinks-rails 5.2.1
• 2f6d50f Merge pull request #39 from yskkin/patch-1
• 7505284 Merge pull request #43 from georgeclaghorn/media-type
• 8da1f63 Prefer ActionDispatch::Response#media_type when it's available
• 2f42a3e Merge pull request #28 from mrhead/set-xhr-redirect-header
• e9ebf31 turbolinks-rails 5.2.0
• 1ce1095 Add source_code_uri metadata
• 56cf714 Set X-XHR-Redirect header
• See full diff in compare view