HS: fix remove [@attr] — consume bracket-close instead of match-kw "]"

match-kw only matches tokens of type "keyword", but ] tokenizes as
bracket-close. This left the ] unconsumed after remove [@foo], causing
the attribute to never be removed. Use (when (= (tp-type) "bracket-close") (adv!))
matching the same pattern parse-add-cmd uses for [attr=val].

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/parser.sx

@@ -1227,7 +1227,7 @@
                   (= (tp-type) "attr")
                   (let
                     ((attr-name (get (adv!) "value")))
-                    (match-kw "]")
+                    (when (= (tp-type) "bracket-close") (adv!))
                     (let
                       ((tgt (if (match-kw "from") (parse-expr) nil)))
                       (list (quote remove-attr) attr-name tgt)))