It is possible to modify perforce-locked graphs.

Repro steps:
1. In a perforce-enabled project, open a locked VFX graph asset (i.e. a file, which is not checked out)
2. Try deleting a node
- #issue 1, modifying the graph should not be possible without checking it out
3. Save the asset
- #issue 2, the file should have a read-only flag and saving without checking it out should not be possible