opal/core: remove Base64 polyfill
opal/core: remove Base64 polyfill

Opal's implementation has been patched and the polyfill is no longer
needed.

Signed-off-by: brian m. carlson <738bdd359be778fee9f0fc4e2934ad72f436ceda@crustytoothpaste.net>

bk2204/daniel-ruby,bk2204/daniel-ruby