LibHTML: Rename Document::normalize() to fixup() and always do it

Node.normalize() is a standard DOM API that coalesces Text nodes.
To avoid clashing with that, rename it to fixup().

This patch also makes it happen automagically as part of parsing.

Libraries/LibHTML/Parser/HTMLParser.cpp

@@ -309,5 +309,7 @@ NonnullRefPtr<Document> parse_html(const StringView& html, const URL& url)
 
     fire_insertion_callbacks(*document);
 
+    document->fixup();
+
     return document;
 }