Remove use of (missing) HashMap.!?.

Author: m-renaud

docs/hash-map.rst

@@ -241,17 +241,12 @@ If you want to provide a default value if the key doesn't exist you can use:
 
 For example::
 
-    import Data.HashMap.Strict ((!?))
-
     HashMap.lookup 1 HashMap.empty
     > Nothing
 
     HashMap.lookup 1 (HashMap.fromList [(1,"one"),(2,"two"),(3,"three")])
     > Just "one"
 
-    > (HashMap.fromList [(1,"one"),(2,"two"),(3,"three")]) !? 1
-    > Just "one"
-
     HashMap.lookupDefault "?" k HashMap.empty
     > "?"