Remove local label error checking

This is actually not necessary, because RGBLINK would warn about missing labels.
Besides, through semi-esoteric ways, it is possible to define more labels in this scope,
and there's no reason to prevent that.

include/asm/output.h

@@ -40,7 +40,6 @@ void out_AbsByteGroup(char *s, int32_t length);
 void out_RelByte(struct Expression *expr);
 void out_RelWord(struct Expression *expr);
 void out_PCRelByte(struct Expression *expr);
-void out_CheckErrors(void);
 void out_WriteObject(void);
 void out_Skip(int32_t skip);
 void out_BinaryFile(char *s);