Update documentation with default value for openLedgerRereplicationGracePeriod config option
### Motivation
`openLedgerRereplicationGracePeriod` default value doc doesn't consistent with the code
### Changes
1. update default value doc for bk_server.conf
Reviewers: Enrico Olivelli <eolivelli@gmail.com>, Michael Marshall <None>, lipenghui <penghui@apache.org>
This closes #2644 from hangc0276/chenhang/fix_openLedgerRereplicationGracePeriod_default_value_doc
diff --git a/conf/bk_server.conf b/conf/bk_server.conf
index 1ae3691..b400899 100755
--- a/conf/bk_server.conf
+++ b/conf/bk_server.conf
@@ -934,9 +934,9 @@
# The number of entries that a replication will rereplicate in parallel.
# rereplicationEntryBatchSize=10
-# The grace period, in seconds, that the replication worker waits before fencing and
+# The grace period, in milliseconds, that the replication worker waits before fencing and
# replicating a ledger fragment that's still being written to upon bookie failure.
-# openLedgerRereplicationGracePeriod=30
+# openLedgerRereplicationGracePeriod=30000
# The time to backoff when replication worker encounters exceptions on replicating a ledger, in milliseconds.
# rwRereplicateBackoffMs=5000
