* nongnu/packages/mozilla.scm (firefox) [arguments]: use the default value of
`--enable-default-toolkit='. The Wayland backend of Firefox is no longer
considered experimental and support for it is included in the official binaries.
* nongnu/packages/mozilla.scm (firefox-wayland): Re-write the package
definition, based upon `ungoogled-chromium-wayland' to avoid re-compiling
Firefox in cases when there is a substitute for `firefox'.
Signed-off-by: Jonathan Brielmaier <jonathan.brielmaier@web.de>