Remove :$CWD param in IO::Path.dir

Fixes RT#132675: https://rt.perl.org/Ticket/Display.html?id=132675

It was never documented and not specced in any released language.
We already have perfectly usable $!CWD for the purpose and the
bug in the ticket was caused precisely by the confusion having
two CWD knobs to tweak brings.

For &dir, We already have two ways to change CWD: $*CWD that'd affect
how given Str arg would be IO::Path-ified as well as $.CWD
attribute on IO::Path objects themselves.

src/core/IO/Path.pm

@@ -549,11 +549,7 @@ my class IO::Path is Cool does IO {
     }
 
     proto method dir(|) {*} # make it possible to augment with multies from modulespace
-    multi method dir(IO::Path:D:
-        Mu :$test = $*SPEC.curupdir,
-        :$CWD = $*CWD,
-    ) {
-
+    multi method dir(IO::Path:D: Mu :$test = $*SPEC.curupdir) {
         CATCH { default {
             fail X::IO::Dir.new(
               :path($.absolute), :os-error(.Str) );
@@ -576,21 +572,21 @@ my class IO::Path is Cool does IO {
 
         my Mu $dirh := nqp::opendir(nqp::unbox_s($.absolute));
         gather {
-           # set $*CWD inside gather for $test.ACCEPTS to use correct
-           # $*CWD the user gave us, instead of whatever $*CWD is
-           # when the gather is actually evaluated. We use a temp var
-           # so that .IO coercer doesn't use the nulled `$*CWD` for
-           # $!CWD attribute and we don't use `temp` for this, because
-           # it's about 2x slower than using a temp var.
-           my $cwd = $CWD.IO;
+          # set $*CWD inside gather for $test.ACCEPTS to use correct
+          # $*CWD the user gave us, instead of whatever $*CWD is
+          # when the gather is actually evaluated. We use a temp var
+          # so that .IO coercer doesn't use the nulled `$*CWD` for
+          # $!CWD attribute and we don't use `temp` for this, because
+          # it's about 2x slower than using a temp var.
+          my $cwd = $!CWD.IO;
           { my $*CWD = $cwd;
 #?if jvm
             for <. ..> -> $elem {
                 $test.ACCEPTS($elem) && (
                   $absolute
                     ?? take IO::Path!new-from-absolute-path(
-                        $abspath ~ $elem,:$!SPEC,:$CWD)
-                    !! take IO::Path.new($path ~ $elem,:$!SPEC,:$CWD)
+                        $abspath ~ $elem,:$!SPEC,:$!CWD)
+                    !! take IO::Path.new($path ~ $elem,:$!SPEC,:$!CWD)
                 );
             }
 #?endif
@@ -602,9 +598,9 @@ my class IO::Path is Cool does IO {
                 nqp::if(
                   $absolute,
                   (take IO::Path!new-from-absolute-path(
-                    nqp::concat($abspath,$str-elem),:$!SPEC,:$CWD)),
+                    nqp::concat($abspath,$str-elem),:$!SPEC,:$!CWD)),
                   (take IO::Path.new(
-                    nqp::concat($path,$str-elem),:$!SPEC,:$CWD)),)));
+                    nqp::concat($path,$str-elem),:$!SPEC,:$!CWD)),)));
             nqp::closedir($dirh);
           }
         }