Update reference for Style/FloatDivision

Follow #9186 (comment).

This PR updates the reference for `Style/FloatDivision`.

The new link is a comprehensive reference that includes the old link address,
so this PR is replacing the URL rather than adding new link.

Author: koic

config/default.yml

@@ -3209,7 +3209,7 @@ Style/ExponentialNotation:
 Style/FloatDivision:
   Description: 'For performing float division, coerce one side only.'
   StyleGuide: '#float-division'
-  Reference: 'https://github.com/rubocop-hq/ruby-style-guide/issues/628'
+  Reference: 'https://blog.rubystyle.guide/ruby/2019/06/21/float-division.html'
   Enabled: true
   VersionAdded: '0.72'
   VersionChanged: <<next>>