[3.12] gh-115921: Change 'equation' to 'expression' in random.rst (GH-115927) (#115928)

In uniform function entry.
(cherry picked from commit de0b4f9)

Co-authored-by: Terry Jan Reedy <[email protected]>

Author: miss-islington

Doc/library/random.rst

@@ -301,7 +301,8 @@ be found in any statistics text.
    ``a <= b`` and ``b <= N <= a`` for ``b < a``.
 
    The end-point value ``b`` may or may not be included in the range
-   depending on floating-point rounding in the equation ``a + (b-a) * random()``.
+   depending on floating-point rounding in the expression
+   ``a + (b-a) * random()``.
 
 
 .. function:: triangular(low, high, mode)