Revert "Also adjust t/xsub_h.t to use $^V." part of 4a88c34 for maint

The error produced in this test, running against perl 5.36.1, is:

Perl API version v1.0.16 of Pie does not match v5.36.0

which doesn't match the expected error when $^V is used because that is
5.36.1.

It's the API version that we're expecting in the output, and that's frozen
at .0 for maint releases (unlike blead, where it incremented for every
release).

ext/XS-APItest/t/xsub_h.t

@@ -117,7 +117,7 @@ foreach $XS_VERSION (undef, @versions) {
 is_deeply([XS_APIVERSION_valid("Pie")], [], "XS_APIVERSION_BOOTCHECK passes");
 is(eval {XS_APIVERSION_invalid("Pie"); 1}, undef,
    "XS_APIVERSION_BOOTCHECK croaks for an invalid version");
-like($@, qr/Perl API version v1.0.16 of Pie does not match \Q$^V\E/a,
+like($@, qr/Perl API version v1.0.16 of Pie does not match v5\.\d+\.\d+/,
      "expected error");
 
 my @xsreturn;