LibJS+LibWeb: Do not return error from VM::create

This never returns an error to propogate, also allowing ErrorOr
to be removed from creating the main thread VM.

Libraries/LibTest/JavaScriptTestRunnerMain.cpp

@@ -183,7 +183,7 @@ int main(int argc, char** argv)
         g_main_hook();
 
     if (!g_vm) {
-        g_vm = MUST(JS::VM::create());
+        g_vm = JS::VM::create();
         g_vm->set_dynamic_imports_allowed(true);
     }