reenabled clear test, made clear working (#5323)

lib/pure/collections/tables.nim

@@ -814,10 +814,13 @@ proc len*[A](t: CountTable[A]): int =
   ## returns the number of keys in `t`.
   result = t.counter
 
-proc clear*[A](t: var CountTable[A] | CountTableRef[A]) =
+proc clear*[A](t: CountTableRef[A]) =
+  ## Resets the table so that it is empty.
+  clearImpl()
+
+proc clear*[A](t: var CountTable[A]) =
   ## Resets the table so that it is empty.
   clearImpl()
-  t.counter = 0
   
 iterator pairs*[A](t: CountTable[A]): (A, int) =
   ## iterates over any (key, value) pair in the table `t`.

tests/collections/ttables.nim

@@ -190,8 +190,6 @@ block zeroHashKeysTest:
   doZeroHashValueTest(toOrderedTable[string,string]({"egg": "sausage"}),
       "", "spam")
 
-# Until #4448 is fixed, these tests will fail
-when false:
 block clearTableTest:
   var t = data.toTable
   assert t.len() != 0