bump rocksdb submodule to latest ceph-reef-v7.9.2

Signed-off-by: Casey Bodley <cbodley@redhat.com>
(cherry picked from commit 87cd54281c88baca423c0e541f71a5e66d719fc4)

diff --git a/src/rocksdb b/src/rocksdb
index 473534bffa129e8f49e25c75020b0190d528572d..9fa4990159853479a222244574ca41202e4c95c1 160000 (submodule)
--- a/src/rocksdb
+++ b/src/rocksdb
@@ -1 +1 @@
-Subproject commit 473534bffa129e8f49e25c75020b0190d528572d
+Subproject commit 9fa4990159853479a222244574ca41202e4c95c1