For 5.34.0, revert the fix for GH #18614 as it introduces a regression.

This reverts the XS code change from March 2021 from commit c71f1f2:
    Make Data::Dumper mark regex output as UTF-8 if needed

retains the new tests, but skips them for Dumpxs.

The change fixed one bug, but introduced another (GH #18764). The fix for
both seems a little too risky this late in the release cycle, so revert to
the v5.32.0 behaviour for the v5.34.0 release itself. Both bugs will be fix
with a CPAN release very soon, which likely will also be in v5.34.1

dist/Data-Dumper/Dumper.pm

@@ -29,7 +29,7 @@ our ( $Indent, $Trailingcomma, $Purity, $Pad, $Varname, $Useqq, $Terse, $Freezer
 our ( @ISA, @EXPORT, @EXPORT_OK, $VERSION );
 
 BEGIN {
-    $VERSION = '2.178'; # Don't forget to set version and release
+    $VERSION = '2.179'; # Don't forget to set version and release
                         # date in POD below!
 
     @ISA = qw(Exporter);
@@ -1476,7 +1476,7 @@ modify it under the same terms as Perl itself.
 
 =head1 VERSION
 
-Version 2.178
+Version 2.179
 
 =head1 SEE ALSO
 

dist/Data-Dumper/Dumper.xs

@@ -651,10 +651,6 @@ dump_regexp(pTHX_ SV *retval, SV *val)
 
     assert(sv_pattern);
 
-    if (SvUTF8(sv_pattern)) {
-        sv_utf8_upgrade(retval);
-    }
-
     rval = SvPV(sv_pattern, rlen);
     rend = rval+rlen;
     slash = rval;

dist/Data-Dumper/t/dumper.t

@@ -1725,6 +1725,9 @@ EOW
   TEST qq(Data::Dumper->Dump([ [qq/\x{41f}/, qr/\x{8b80}/, qr/\x{41f}/] ])),
     "string with Unicode + regexp with Unicode";
 
+  SKIP_TEST "skipped, pending fix for github #18764";
+  last;
+
   TEST qq(Data::Dumper->Dumpxs([ [qq/\x{41f}/, qr/\x{8b80}/, qr/\x{41f}/] ])),
     "string with Unicode + regexp with Unicode, XS"
     if $XS;