Fix CanFocusWithScrollbarsOnly

It stopped working behaving correctly after 2.0.0:
Textualize/textual#5605

Still there is a know issue:
Textualize/textual#5609

Author: mzebrak

clive/__private/ui/screens/operations/governance_operations/common_governance/governance_actions.py

@@ -86,7 +86,7 @@ def compose(self) -> ComposeResult:
             yield Static("Action", id="action-row")
             yield Static(self.NAME_OF_ACTION, id="action-name-row")
 
-    async def on_mount(self) -> None:  # type: ignore[override]
+    async def on_mount(self) -> None:
         await self.mount_operations_from_cart()
 
     async def add_row(self, identifier: str, *, vote: bool = False, pending: bool = False) -> None:

clive/__private/ui/widgets/scrolling.py

@@ -13,17 +13,9 @@ class CanFocusWithScrollbarsOnly(CliveWidget, AbstractClassMessagePump):
     Inherit from this class to make a widget focusable only when any scrollbar is active.
     """
 
-    def on_mount(self) -> None:
-        self.__enable_focus_only_when_scrollbar_is_active()
-
-    def watch_show_vertical_scrollbar(self) -> None:
-        self.__enable_focus_only_when_scrollbar_is_active()
-
-    def watch_show_horizontal_scrollbar(self) -> None:
-        self.__enable_focus_only_when_scrollbar_is_active()
-
-    def __enable_focus_only_when_scrollbar_is_active(self) -> None:
-        self.can_focus = any(self.scrollbars_enabled)
+    def allow_focus(self) -> bool:
+        # Known issue: https://github.com/Textualize/textual/issues/5609
+        return any(self.scrollbars_enabled)
 
 
 class ScrollablePartFocusable(VerticalScroll, CanFocusWithScrollbarsOnly):