test: cover duplicate method parameters

tests/typecheck_method_compat_duplicate_param_bad.claro

@@ -0,0 +1,8 @@
+CLASS Player
+    TEACH greet TAKES name, name
+        SAY name
+    LEARNED
+ENDCLASS
+
+NEW Player player
+CALL player.greet WITH "Ada", "Grace"

tests/typecheck_method_duplicate_param_bad.claro

@@ -0,0 +1,8 @@
+CLASS Player
+    TEACH greet name, name
+        SAY name
+    END
+END
+
+NEW Player player
+DO player.greet "Ada", "Grace"