Update docs for accountPatchReviewDb

This updates the doc for accountPatchReviewDb to mention you have to
use a different db name instead of gerrit's db

Change-Id: I2742bfd6d53c80644e6fdee41c07a28c30d087c9
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index dd2745b..75094a6 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -33,6 +33,9 @@
 Changing this parameter requires to migrate database using the
 link:pgm-MigrateAccountPatchReviewDb.html[MigrateAccountPatchReviewDb] program.
 Migration cannot be done while the server is running.
++
+Also note that the db_name has to be a new db and not reusing gerrit's own review database,
+otherwise gerrit's init will remove the table.
 
 ----
 [accountPatchReviewDb]