screenrc: drop keybindings G (google) + H (heise.de)

Those vendor specific configs shouldn't be shipped as such,
especially since we overwrite the default log function
(https://www.gnu.org/software/screen/manual/screen.html#Logging)
which defaults to 'H', so conflicting with our HeiseTicker
binding. Therefore remove it.

Thanks: Ralf Moll for reporting