mesa: remove old comments

mesa: remove old comments

Note: the default value for EmitCondCodes is FALSE.  This means the GLSL
compiler will emit code like this:

SEQ TEMP[0].x, A, B;
IF TEMP[0].x;
   ...
ENDIF

But if EmitCondCodes is TRUE, condition codes will be used instead:

SEQ.C TEMP[0].x, A, B;
IF (NE.xxxx);
   ...
ENDIF