Begone foul if who changeth keyword to symbol
Begone foul if who changeth keyword to symbol

Currently we allow a string to be annotated with
either keyword or symbol. Instead we should force the
user to select symbol, as what is a keyword but
a symbol in a specific package.

PiperOrigin-RevId: 340232584

qitab/cl-protobufs,qitab/cl-protobufs