Fix div docstring to describe division, after #33040 (#33703)

It looks like in #33040 the `div` docstring was accidentally incorrectly copied from the `rem` docstring, so it currently describes the `rem` operation, not `div`.

This commit changes that docstring to correctly describe integer division with custom rounding.

Author: NHDaly

base/div.jl

@@ -3,10 +3,10 @@
 """
     div(x, y, r::RoundingMode=RoundToZero)
 
-Compute the remainder of `x` after integer division by `y`, with the quotient rounded
-according to the rounding mode `r`. In other words, the quantity
+The quotient from Euclidean division. Computes x/y, rounded to an integer according
+to the rounding mode `r`. In other words, the quantity
 
-    y*round(x/y,r)
+    round(x/y,r)
 
 without any intermediate rounding.