[Perl/perl5] 81a914: toke.c - silence build warning for non DEBUGGING mode

[Yves Orton via perl5-changes]

  Branch: refs/heads/yves/fix_unused_var_warning_toke_c
  Home:   https://github.com/Perl/perl5
  Commit: 81a914cab947d11c2c4dca92cc561bc1120722f7
      
https://github.com/Perl/perl5/commit/81a914cab947d11c2c4dca92cc561bc1120722f7
  Author: Yves Orton <demer...@gmail.com>
  Date:   2022-09-24 (Sat, 24 Sep 2022)

  Changed paths:
    M toke.c

  Log Message:
  -----------
  toke.c - silence build warning for non DEBUGGING mode

A previous commit introduced the variable 'bool syntax_error' which
was only used under DEBUGGING, which produced unused variable
warnings on "production" builds. This reworks the code to not need
the variable at all.

Warning fixed:

    toke.c: In function ‘Perl_yyerror_pvn’:
    toke.c:12662:14: warning: unused variable ‘syntax_error’ [-Wunused-variable]
    12662 |         bool syntax_error = 
PERL_PARSE_IS_SYNTAX_ERROR(PL_error_count);
          |              ^~~~~~~~~~~~