refactor!: keep one name for pending updates, drop the alias

This driver implemented get_pending_updates and then carried
get_available_updates as a one-line alias, because netOrk's API only ever called
the latter. Two names for one thing, with the driver bridging the gap.

napalm-device-types v1.0 collapses them onto get_available_updates — the name
four drivers and every netOrk call site already used — so the alias has nothing
left to bridge.

BREAKING CHANGE: get_pending_updates is gone; call get_available_updates.

The seven pre-existing test failures in this repo are untouched and unrelated;
see netork#110.

napalm_linux/linux.py

@@ -1019,7 +1019,7 @@ class LinuxDriver(OSDriver):
         success = not any(kw in low for kw in ("error:", "failed", "not found", "is not installed", "no packages"))
         return {"success": success, "output": raw.strip()}
 
-    def get_pending_updates(self) -> list[UpdateDict]:
+    def get_available_updates(self) -> list[UpdateDict]:
         if self._pkg_manager == "apt":
             return self._get_updates_apt()
         if self._pkg_manager in ("dnf", "yum"):
@@ -1032,10 +1032,6 @@ class LinuxDriver(OSDriver):
             f"Package manager '{self._pkg_manager}' is not supported"
         )
 
-    def get_available_updates(self) -> list[UpdateDict]:
-        """Alias for get_pending_updates(); called by the netork API backend."""
-        return self.get_pending_updates()
-
     def get_device_warnings(self) -> List[dict[str, Any]]:
         """Return warning dicts for issues detected on this device.