With C23 (as upcoming GCC 15 will default to), `void yyerror()` is
the same as `void yyerror(void)`, i.e. `yyerror` takes no arguments.
Fix the prototype given we *do* call it with an error string:
```
pgen.p/parser.tab.c: In function ‘yyparse’:
pgen.p/parser.tab.c:1104:7: error: too many arguments to function ‘yyerror’
1104 | yyerror (YY_("syntax error"));
| ^~~~~~~
../test cases/frameworks/8 flex/parser.y:3:12: note: declared here
3 | extern int yyerror();
| ^~~~~~~
pgen.p/parser.tab.c:1215:3: error: too many arguments to function ‘yyerror’
1215 | yyerror (YY_("memory exhausted"));
| ^~~~~~~
../test cases/frameworks/8 flex/parser.y:3:12: note: declared here
3 | extern int yyerror();
| ^~~~~~~
```
Bug: https://bugs.gentoo.org/946625
Sam James