Ignore Ruby warnings about deprecated things in Puppet code

On Debian unstable these were being printed:

/usr/lib/ruby/vendor_ruby/puppet/util.rb:461: warning: URI.escape is obsolete
/usr/lib/ruby/vendor_ruby/puppet/file_system/file_impl.rb:80: warning: Using the last argument as keyword parameters is deprecated

Workaround-for: https://bugs.debian.org/955532