Fix documentation for cljs.core/filter

Copied correct documentation from clojuredocs.org. The previous documentation
seemed to be the one for `cljs.core/keep`.

docs/cljs.core_filter.cljsdoc

@@ -2,15 +2,15 @@
 cljs.core/filter
 
 ===== Signature
-[f]
-[f coll]
+[pred]
+[pred coll]
 
 ===== Description
 
-Returns a lazy sequence of the non-nil results of `(f item)`. Note, this means
-false return values will be included.
+Returns a lazy sequence of the items in coll for which `(pred item)` returns
+logical true.
 
-`f` must be free of side-effects.
+`pred` must be free of side-effects.
 
 Returns a transducer when no collection is provided.