raft: Upgrade cockroachdb/pebble package

The recent version does not work with 32-bit platforms. This commit bumps that package version to higher version. The bug was fixed in: https://github.com/cockroachdb/pebble/issues/2853

It breaks our build at https://dev.gitlab.org/gitlab/omnibus-gitlab/-/pipelines/333618/failures

As the latest pebble version is not compatible with dragonboat. There are some minor changes in pebble. So, we have no choice but to fork dragonboat to upgrade the dependency: gl-gitaly/dragonboat@725bd577. All tests in dragonboat passed.

We'll upstream this dependency bump later.