Add warning about Reminder bot issues on Matrix Authentication Service docs page

Author: spantaleev

docs/configuring-playbook-matrix-authentication-service.md

@@ -55,6 +55,8 @@ This section details what you can expect when switching to the Matrix Authentica
 
 - ❌ **Some services experience issues when authenticating via MAS**:
 
+  - [Reminder bot](configuring-playbook-bot-matrix-reminder-bot.md) seems to be losing some of its state on each restart and may reschedule old reminders once again
+
 - ❌ **Encrypted appservices** do not work yet (related to [MSC4190](https://github.com/matrix-org/matrix-spec-proposals/pull/4190) and [PR 17705 for Synapse](https://github.com/element-hq/synapse/pull/17705)), so all bridges/bots that rely on encryption will fail to start (see [this issue](https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3658) for Hookshot). You can use these bridges/bots only if you **keep end-to-bridge encryption disabled** (which is the default setting).
 
 - ⚠️ [Migrating an existing Synapse homeserver to Matrix Authentication Service](#migrating-an-existing-synapse-homeserver-to-matrix-authentication-service) is **possible**, but requires **some playbook-assisted manual work**. Migration is **reversible with no or minor issues if done quickly enough**, but as users start logging in (creating new login sessions) via the new MAS setup, disabling MAS and reverting back to the Synapse user database will cause these new sessions to break.