Bug 1890905 - Avoid basic_string_view<unsigned char> from ever being picked as a possibility for NewStringCopy. r=spidermonkey-reviewers,dminor

It's not a valid type.

Differential Revision: https://phabricator.services.mozilla.com/D207231

js/src/vm/StringType.h

@@ -1737,7 +1737,9 @@ inline JSLinearString* NewStringCopy(
 }
 
 /* Copy a counted string and GC-allocate a descriptor for it. */
-template <js::AllowGC allowGC, typename CharT>
+template <
+    js::AllowGC allowGC, typename CharT,
+    typename std::enable_if_t<!std::is_same_v<CharT, unsigned char>>* = nullptr>
 inline JSLinearString* NewStringCopy(
     JSContext* cx, std::basic_string_view<CharT> s,
     js::gc::Heap heap = js::gc::Heap::Default) {