[Perl/perl5] ebf36c: dump.c - add missing cast

[Yves Orton via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: ebf36c261956869e9ac9fea13c6ebe49e977d85d
      
https://github.com/Perl/perl5/commit/ebf36c261956869e9ac9fea13c6ebe49e977d85d
  Author: Yves Orton <demer...@gmail.com>
  Date:   2022-10-30 (Sun, 30 Oct 2022)

  Changed paths:
    M dump.c

  Log Message:
  -----------
  dump.c - add missing cast

In 06d92f00e810ad2f12b8fb9c1adf0d22765d6ccc we added the CV_FROM_REF()
macros, these macros assume the argument is an SV, so the gv prequires
a cast. The argument was cast to SV* in another case, so I am adding the
same fix here.

Silences the following warning:

    dump.c: In function ‘S_gv_display’:
    dump.c:880:58: warning: initialization of ‘SV *’ {aka ‘struct sv *’} from
    incompatible pointer type ‘GV *’ {aka ‘struct gv *’} 
[-Wincompatible-pointer-types]
      880 |                     SvPV_nolen_const(cv_name(CV_FROM_REF(gv), name, 
0)));
          |                                                          ^~
    sv.h:1912:42: note: in definition of macro ‘SvPV_flags_const_nolen’
     1912 |    ((const char*) Perl_SvPV_helper(aTHX_ sv, NULL, flags, 
SvPVnormal_type_, \
          |                                          ^~
    dump.c:880:21: note: in expansion of macro ‘SvPV_nolen_const’
      880 |                     SvPV_nolen_const(cv_name(CV_FROM_REF(gv), name, 
0)));
          |                     ^~~~~~~~~~~~~~~~
    dump.c:880:38: note: in expansion of macro ‘cv_name’
      880 |                     SvPV_nolen_const(cv_name(CV_FROM_REF(gv), name, 
0)));
          |                                      ^~~~~~~
    handy.h:136:27: note: in expansion of macro ‘xV_FROM_REF’
      136 | #define CV_FROM_REF(ref)  xV_FROM_REF(CV, ref)
          |                           ^~~~~~~~~~~
    dump.c:880:46: note: in expansion of macro ‘CV_FROM_REF’
      880 |                     SvPV_nolen_const(cv_name(CV_FROM_REF(gv), name, 
0)));