trivial typo in ?colorRampPalette

The help page for colorRampPalette reads in part

    alpha: logical: should alpha channel (opacity) values should be
           returned?

which should probably be

     alpha: logical: should alpha channel (opacity) values be returned?

This is in (2016-02-09 r70138) -- sorry if I missed an update.

   cheers
     Ben Bolker