Move savepoint creation back on the subscription store

This reverts commit 194f387.

We discussed that we dont want to ensure exactly once delivery for external projections. Adding transaction logic via traits for the projections increases logic there. And while with alot of effort we could bring exactly once delivery to work for most cases php could still decide to die in the small timeframe where we commit the one transaction and then the second. So there is no gurantee except when using a dedicated store: neos/neos-development-collection#5377

src/DoctrineDbalContentGraphProjection.php

@@ -62,7 +62,6 @@
 use Neos\ContentRepository\Core\Feature\WorkspaceRebase\Event\WorkspaceRebaseFailed;
 use Neos\ContentRepository\Core\Feature\WorkspaceRebase\Event\WorkspaceWasRebased;
 use Neos\ContentRepository\Core\Infrastructure\DbalSchemaDiff;
-use Neos\ContentRepository\Core\Infrastructure\ProjectionTransactionTrait;
 use Neos\ContentRepository\Core\NodeType\NodeTypeName;
 use Neos\ContentRepository\Core\Projection\ContentGraph\ContentGraphProjectionInterface;
 use Neos\ContentRepository\Core\Projection\ContentGraph\ContentGraphReadModelInterface;
@@ -81,8 +80,6 @@
  */
 final class DoctrineDbalContentGraphProjection implements ContentGraphProjectionInterface
 {
-    use ProjectionTransactionTrait;
-
     use ContentStream;
     use NodeMove;
     use NodeRemoval;