patch(_update_bundle.yaml): Alphabetically sort snap revision list (#243

)

## Issue

The workflow mistakenly created PRs for updating the snaps list because
of ordering, even though the revisions itself didn't change. This is
because, for python:

```
> {"packages": ["snap1", "snap2", "snap3"]} != {"packages": ["snap1", "snap3", "snap2"]}
True
```
then, `snaps != old_snaps` was being set to true every time, and the
output of `updates_available` was mistakenly being set to `true`
## Solution

Sort the snaps list. See test runs: 

postgresql:
canonical/postgresql-bundle@d5056b5
mysql:
canonical/mysql-bundle@4269833

python/cli/data_platform_workflows_cli/update_bundle.py

@@ -16,7 +16,7 @@
 from . import github_actions
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(order=True, frozen=True)
 class Snap:
     name: str
     revision: int
@@ -272,7 +272,7 @@ def main():
             file.write(yaml_string)
 
     if len(bundle_snaps) > 0:
-        snaps_data = {"packages": [dataclasses.asdict(snap) for snap in bundle_snaps]}
+        snaps_data = {"packages": [dataclasses.asdict(snap) for snap in sorted(bundle_snaps)]}
         try:
             old_snaps_data = yaml.safe_load(pathlib.Path(SNAPS_YAML_PATH).read_text())
         except FileNotFoundError: