remove the alias definition for symbolic color names

When using symbolic color names, we can drop the redefinition of the fill and draw colors.

This greatly reduces the file size. A fallback mechanism ensures the definitions are done as usual if either

 1. the maximal number of colors are exhausted or
 1. symbolic color names are switched off.
This is unnecessary, the NEWS stay header-less until a release (e.g., https://github.com/mbergner/tikzDevice/blob/5536d73e77b16ee4adb84a8ea196e9d4f3f0d2bd/NEWS.md).