Documented that WAL can still be written after memory-snapshot-on-shutdown (#15179)

Documented that WAL can still be written after memory-snapshot-on-shutdown - #10824

Co-authored-by: Björn Rabenstein <github@rabenste.in>
Signed-off-by: gopi <gopi.singaravelan.k@gmail.com>

---------

Signed-off-by: Gopi-eng2202 <gopi.singaravelan.k@gmail.com>
Signed-off-by: gopi <gopi.singaravelan.k@gmail.com>
Co-authored-by: Björn Rabenstein <github@rabenste.in>

docs/feature_flags.md

@@ -23,9 +23,8 @@ Exemplar storage is implemented as a fixed size circular buffer that stores exem
 
 `--enable-feature=memory-snapshot-on-shutdown`
 
-This takes the snapshot of the chunks that are in memory along with the series information when shutting down and stores
-it on disk. This will reduce the startup time since the memory state can be restored with this snapshot and m-mapped
-chunks without the need of WAL replay.
+This takes a snapshot of the chunks that are in memory along with the series information when shutting down and stores it on disk. This will reduce the startup time since the memory state can now be restored with this snapshot 
+and m-mapped chunks, while a WAL replay from disk is only needed for the parts of the WAL that are not part of the snapshot.
 
 ## Extra scrape metrics