Changing WorkfileQueryspace_ReleaseEntry assert to check...

Changing WorkfileQueryspace_ReleaseEntry assert to check querySpaceNestingLevel == 0 when we release the entry.

src/backend/utils/workfile_manager/workfile_queryspace.c

@@ -339,7 +339,7 @@ WorkfileQueryspace_ReleaseEntry(void)
 				session_id, command_count);
 	}
 
-	Assert(querySpaceNestingLevel >= 0);
+	Assert(querySpaceNestingLevel == 0);
 }
 
 /*