Tidy up the docstring of Widget.scroll_page_left

Delivering on a promise made in Textualize#1920.

src/textual/widget.py

@@ -1946,12 +1946,11 @@ def scroll_page_left(
         """Scroll one page left.
 
         Args:
-            animate: Animate scroll. Defaults to True.
-            speed: Speed of scroll if animate is True. Or None to use duration.
-            duration: Duration of animation, if animate is True and speed is None.
-            easing: An easing method for the scrolling animation. Defaults to "None",
-                which will result in Textual choosing the configured default scrolling easing function.
-            force: Force scrolling even when prohibited by overflow styling. Defaults to `False`.
+            animate: Animate scroll.
+            speed: Speed of scroll if animate is `True`; or `None` to use `duration`.
+            duration: Duration of animation, if `animate` is `True` and `speed` is `None`.
+            easing: An easing method for the scrolling animation.
+            force: Force scrolling even when prohibited by overflow styling.
         """
         if speed is None and duration is None:
             duration = 0.3