Update doc comment in tactic Util.hs

Author: Ailrun

plugins/hls-tactics-plugin/test/Utils.hs

@@ -61,7 +61,7 @@ codeActionTitle (InR(CodeAction title _ _ _ _ _ _ _)) = Just title
 mkTest
     :: Foldable t
     => String  -- ^ The test name
-    -> FilePath  -- ^ The file basename to load
+    -> FilePath  -- ^ The file name stem (without extension) to load
     -> Int  -- ^ Cursor line
     -> Int  -- ^ Cursor columnn
     -> t ( Bool -> Bool   -- Use 'not' for actions that shouldnt be present