Ignore URI::RFC3986_PARSER.escape deprecation warning

`uri` switched the default parser from RFC2396 to RFC3986. The new parser emits a deprecation
warning on a few methods and delegates them to RFC2396. See ruby/uri#114.

The selenium-webdriver gem [calls `URI::RFC3986_PARSER.escape`][webdriver-callsite], which is now deprecated.
Until this is fixed in selenium-webdriver, ignore the warning.

[webdriver-callsite]: https://github.com/SeleniumHQ/selenium/blob/trunk/rb/lib/selenium/webdriver/remote/bridge.rb#L679

test/test_helper.rb

@@ -48,6 +48,9 @@ module Warning
   class << self
     def warn(message)
       return super if message.start_with?("Rack::Handler is deprecated")
+      # To be removed once warning is fixed in selenium-webdriver
+      # This is noisy, so ignoring completely for now.
+      return if message.match?("URI::RFC3986_PARSER.escape is obsoleted.")
 
       raise message.to_s
     end