Remove mention of TimeLineID update from comments

Commit 4a92a1c3d removed the TimeLineID update from RecoveryInProgress,
update comments accordingly.

Author: Amul Sul <sulamul@gmail.com>
Discussion: https://postgr.es/m/CAAJ_b96wyzs8N45jc-kYd-bTE02hRWQieLZRpsUtNbhap7_PuQ@mail.gmail.com

src/backend/access/transam/xlog.c

@@ -8391,8 +8391,8 @@ PerformRecoveryXLogAction(void)
  * Unlike testing InRecovery, this works in any process that's connected to
  * shared memory.
  *
- * As a side-effect, we initialize the local TimeLineID and RedoRecPtr
- * variables the first time we see that recovery is finished.
+ * As a side-effect, we initialize the local RedoRecPtr variable the first
+ * time we see that recovery is finished.
  */
 bool
 RecoveryInProgress(void)

src/backend/postmaster/checkpointer.c

@@ -384,11 +384,7 @@ CheckpointerMain(void)
 			bool		ckpt_performed = false;
 			bool		do_restartpoint;
 
-			/*
-			 * Check if we should perform a checkpoint or a restartpoint. As a
-			 * side-effect, RecoveryInProgress() initializes TimeLineID if
-			 * it's not set yet.
-			 */
+			/* Check if we should perform a checkpoint or a restartpoint. */
 			do_restartpoint = RecoveryInProgress();
 
 			/*