method, method, method, method, method

This commit resolves the problem when “method” is repeated 20 times
needlessly. It was assumed that .unique is going to do the trick, but
in reality it's an array of 1-element arrays, so we have to slip it.

There was a ticket for that issue but I can't find it.

htmlify.p6

@@ -880,7 +880,7 @@ sub write-sub-index(:$kind, :$category, :&summary = {Nil}) {
             .grep({$category ⊆ .categories})\ # XXX
             .categorize(*.name).sort(*.key)>>.value
             .map({[
-                .map({.subkinds // Nil}).unique.join(', '),
+                .map({slip .subkinds // Nil}).unique.join(', '),
                 pod-link(.[0].name, .[0].url),
                 .&summary
             ]})
@@ -893,10 +893,8 @@ sub write-kind($kind) {
     $*DR.lookup($kind, :by<kind>)
         .categorize({.name})
         .kv.map: -> $name, @docs {
-            my @subkinds = @docs.map({.subkinds}).unique;
-            my $subkind = @subkinds.squish(with => &infix:<~~>) == 1
-                          ?? @subkinds.list[0]
-                          !! $kind;
+            my @subkinds = @docs.map({slip .subkinds}).unique;
+            my $subkind = @subkinds == 1 ?? @subkinds[0] !! $kind;
             my $pod = pod-with-title(
                 "$subkind $name",
                 pod-block("Documentation for $subkind $name, assembled from the following types:"),