Fix test case name

Author: hrsh7th

test/Async/Promise.vimspec

@@ -860,7 +860,7 @@ Describe Async.Promise
       Assert Equals(error, result)
     End
 
-    It should not call when promise catched
+    It should not call when catched rejected promise
       let l = l:
       call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })
 
@@ -869,7 +869,7 @@ Describe Async.Promise
       Assert KeyNotExists(l, 'result')
     End
 
-    It should not call when promise catched
+    It should not call when catched thrown error
       let l = l:
       call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })