Revert "[MERGE] add+use PL_curstackinfo->si_cxsubix field"v5.31.4

This reverts commit d2cd363728088adada85312725ac9d96c29659be, reversing
changes made to 068b48acd4bdf9e7c69b87f4ba838bdff035053c.

This change breaks installing Test::Deep:

...
not ok 37 - Test 'isa eq' completed
ok 38 - Test 'isa eq' no premature diagnostication
...

1 files changed, 0 insertions, 1 deletions

diff --git a/scope.c b/scope.c
index c6616440f6..9b1393c69d 100644
--- a/scope.c
+++ b/scope.c
@@ -82,7 +82,6 @@ Perl_new_stackinfo(pTHX_ I32 stitems, I32 cxitems)
     si->si_next = 0;
     si->si_cxmax = cxitems - 1;
     si->si_cxix = -1;
-    si->si_cxsubix = -1;
     si->si_type = PERLSI_UNDEF;
     Newx(si->si_cxstack, cxitems, PERL_CONTEXT);
     /* Without any kind of initialising CX_PUSHSUBST()