Remove support for Google Spanner database. (#105846)

* Remove support for Google Spanner database.

pkg/services/folder/folderimpl/folder.go

@@ -168,10 +168,6 @@ func (s *Service) DBMigration(db db.DB) {
 				SELECT uid, org_id, title, created, updated FROM dashboard WHERE is_folder = true
 				ON CONFLICT(uid, org_id) DO UPDATE SET title=excluded.title, updated=excluded.updated
 			`)
-		} else if db.GetDialect().DriverName() == migrator.Spanner {
-			// We may eventually make this migration work with Spanner, but for now don't do anything.
-			// We intend to store dashboards and folders only in unified storage when using spanner.
-			deleteOldFolders = false
 		} else {
 			// covered by UQE_folder_org_id_uid
 			_, err = sess.Exec(`

pkg/services/folder/folderimpl/sqlstore.go

@@ -620,7 +620,7 @@ func (ss *FolderStoreImpl) GetDescendants(ctx context.Context, orgID int64, ance
 
 func getFullpathSQL(dialect migrator.Dialect) string {
 	escaped := `\/`
-	if dialect.DriverName() == migrator.MySQL || dialect.DriverName() == migrator.Spanner {
+	if dialect.DriverName() == migrator.MySQL {
 		escaped = `\\/`
 	}
 	concatCols := make([]string, 0, folder.MaxNestedFolderDepth)