Avoid reading add-ons twice unnecessarily (#5846)

So far a store reload lead to a reload of all add-ons twice, usually
causing two messages in quick succession:
```
2025-04-25 17:01:05.058 INFO (MainThread) [supervisor.store] Loading add-ons from store: 91 all - 0 new - 0 remove
2025-04-25 17:01:05.058 INFO (MainThread) [supervisor.store] Loading add-ons from store: 91 all - 0 new - 0 remove
```

This is because when repository changes are detected, `reload()` calls
`load()` which then calls `update_repositories()` which ends up calling
`_read_addons()`, while `reload()` itself calls `_read_addons()` after
`load()` as well.

One way to fix this would be to simply remove the `_read_addons()` call
in `reload()`.

However, it seems the `update_repositories()` call (via `load()`)
is not necessary at all, as we don't add new store repositories in
`reload()`, and we already made sure the built-ins are present on
startup.

So simply call `data.update()` to update the store data cache, as it
was the case before #2225. There is no apparent reason documented why
`data.update()` was changed to a `load()` call. It might be to ensure
regularly that built-in repositories are still in the list of store
repositories. But this type of regular invariant check is often harmful
as it might hide bugs in other places.

Supervisor will still call `update_repositories()` in `load()` to
ensure all built-in repositories are present, just in case the local
configuration file got modified or corrupted.

supervisor/store/__init__.py

@@ -116,7 +116,7 @@ class StoreManager(CoreSysAttributes, FileConfiguration):
             )
 
             # read data from repositories
-            await self.load()
+            await self.data.update()
             await self._read_addons()
 
     @Job(