Simplify sub index candidates

Named parameters can be optional and still expected.  This is
different from methods, where unexpected nameds are just ignored.

src/core.c/Cool.pm6

@@ -448,24 +448,16 @@ multi sub flip(Cool $s --> Str:D) { $s.flip }
 
 proto sub index($, $, $?, *%) {*}
 multi sub index(Cool:D $s,
-  Cool:D $needle, :i(:$ignorecase)!, :m(:$ignoremark) --> Int:D) {
+  Cool:D $needle, :i(:$ignorecase), :m(:$ignoremark) --> Int:D) {
     $s.Str.index($needle.Str, :$ignorecase, :$ignoremark)
 }
-multi sub index(Cool:D $s, Cool:D $needle, :m(:$ignoremark)!  --> Int:D) {
-    $s.Str.index($needle.Str, :$ignoremark)
-}
 multi sub index(Cool:D $s, Cool:D $needle --> Int:D) {
     $s.Str.index($needle.Str)
 }
-
 multi sub index(Cool:D $s,
-  Cool:D $needle, Cool:D $pos, :i(:$ignorecase)!, :m(:$ignoremark) --> Int:D) {
+  Cool:D $needle, Cool:D $pos, :i(:$ignorecase), :m(:$ignoremark) --> Int:D) {
     $s.Str.index($needle.Str,$pos.Int, :$ignorecase, :$ignoremark)
 }
-multi sub index(Cool:D $s,
-  Cool:D $needle, Cool:D $pos, :m(:$ignoremark)!  --> Int:D) {
-    $s.Str.index($needle.Str,$pos.Int, :$ignoremark)
-}
 multi sub index(Cool:D $s, Cool:D $needle, Cool:D $pos --> Int:D) {
     $s.Str.index($needle.Str,$pos.Int)
 }