Update finally.md

It seems that the arguments section was copied over from where/filter. It threw me off for a moment...

Author: nelsonlaquet

doc/api/core/operators/finally.md

@@ -4,14 +4,10 @@
 Invokes a specified action after the source observable sequence terminates gracefully or exceptionally.  There is an alias called `finallyAction` for browsers <IE9
 
 #### Arguments
-1. `predicate` *(`Function`)*: A function to test each source element for a condition;  The callback is called with the following information:
-    1. the value of the element
-    2. the index of the element
-    3. the Observable object being subscribed
-2. `[thisArg]` *(`Any`)*: Object to use as `this` when executing the predicate.
+1. `action` *(`Function`)*: A function to invoke after the source observable sequence terminates.
 
 #### Returns
-*(`Observable`)*: An observable sequence that contains elements from the input sequence that satisfy the condition.
+*(`Observable`)*: The source sequence with the side-effecting behavior applied.
 
 #### Example
 ```js