doc: improve docstrings for pipe operators (#13864)

This PR updates the pipe operator docstrings for accurracy and
helpfulness. Such operators are not idiomatic Haskell, so the old text
was incorrect, and it's better to explain the behavior than to reference
other languages anyway.

Author: david-christiansen

src/Init/Notation.lean

@@ -514,9 +514,10 @@ macro_rules
   | `(bif $c then $t else $e) => `(cond $c $t $e)
 
 /--
-Haskell-like pipe operator `<|`. `f <| x` means the same as `f x`,
-except that it parses `x` with lower precedence, which means that `f <| g <| x`
-is interpreted as `f (g x)` rather than `(f g) x`.
+A pipe operator that feeds values from the right into functions on the left.
+
+`f <| x` means the same as `f x`, except that it parses `x` with lower precedence, which means that
+`f <| g <| x` is interpreted as `f (g x)` rather than `(f g) x`.
 -/
 syntax:min term " <| " term:min : term
 
@@ -538,8 +539,9 @@ macro_rules
       `($f $a)
 
 /--
-Haskell-like pipe operator `|>`. `x |> f` means the same as `f x`,
-and it chains such that `x |> f |> g` is interpreted as `g (f x)`.
+A pipe operator that feeds values from the left into functions on the right.
+
+`x |> f` means the same as `f x`, and it chains such that `x |> f |> g` is interpreted as `g (f x)`.
 -/
 syntax:min term " |> " term:min1 : term