Fix luacheck warnings in builtin/common/tests (#10322)

.luacheckrc

@@ -72,3 +72,11 @@ files["builtin/mainmenu"] = {
 		"PLATFORM",
 	},
 }
+
+files["builtin/common/tests"] = {
+	read_globals = {
+		"describe",
+		"it",
+		"assert",
+	},
+}