Improved wording

Co-authored-by: Rodrigo Girão Serrão <5621605+rodrigogiraoserrao@users.noreply.github.com>

src/textual/widgets/_header.py

@@ -74,7 +74,7 @@ class HeaderClock(HeaderClockSpace):
         """Render the header clock.
 
         Returns:
-            The value to render.
+            The rendered clock.
         """
         return Text(datetime.now().time().strftime("%X"))