clean up deprecated stuff and unused imports in tests (#13059)

tests/method/mmultim3.nim

@@ -1,5 +1,5 @@
 type
-    TObj* = object {.inheritable.}
+    TObj* {.inheritable.} = object
 
 var myObj* : ref TObj
 

tests/method/tmultimjs.nim

@@ -9,7 +9,7 @@ hello
 
 # tmultim1
 type
-  Expression = ref object {.inheritable.}
+  Expression {.inheritable.} = ref object
   Literal = ref object of Expression
     x: int
   PlusExpr = ref object of Expression
@@ -69,4 +69,4 @@ var s:ref Test = newTest()
 #doesn't work
 for z in 1..4:
   s.doMethod()
-  break
+  break