fix(test): allow delete random snapshot action (kopia#3987)

Addresses failure introduced in kopia#3963

Change: allow `delete-random-snapID` action in the function `tryDeleteAction`.
Test: Manual local run was successful.

tests/robustness/multiclient_test/multiclient_test.go

@@ -239,13 +239,14 @@ func tryRandomAction(ctx context.Context, t *testing.T, opts engine.ActionOpts)
 }
 
 // tryDeleteAction runs the given delete action,
-// delete-files or delete-random-subdirectory
+// delete-files or delete-random-subdirectory or delete-random-snapID
 // with options and masks no-op errors, and asserts when called for any other action.
 func tryDeleteAction(ctx context.Context, t *testing.T, action engine.ActionKey, actionOpts map[string]string) {
 	t.Helper()
 	eligibleActionsList := []engine.ActionKey{
 		engine.DeleteDirectoryContentsActionKey,
 		engine.DeleteRandomSubdirectoryActionKey,
+		engine.DeleteRandomSnapshotActionKey,
 	}
 	require.Contains(t, eligibleActionsList, action)