[ci skip] Fix 4.2 release notes rendered display.
[ci skip] Fix 4.2 release notes list items. [Matthew Draper & Juanito Fatas]
Force encoding of US-ASCII to UTF-8 in unescape_uri.

Because URI paths may contain non US-ASCII characters we need to force
the encoding of any unescaped URIs to UTF-8 if they are US-ASCII.
This essentially replicates the functionality of the monkey patch to
URI.parser.unescape in active_support/core_ext/uri.rb.

Fixes #16104.