Inactive users to be removed from ARI WG

According to the rules for inactivity defined in [RFC-0025](https://github.com/cloudfoundry/community/blob/main/toc/rfc/rfc-0025-define-criteria-and-removal-process-for-inactive-members.md), the following users should be removed from ARI approvers/reviewers/bots:
- @dennisjbell

According to the [revocation policy in the RFC](https://github.com/cloudfoundry/community/blob/main/toc/rfc/rfc-0025-define-criteria-and-removal-process-for-inactive-members.md#remove-the-membership-to-the-cloud-foundry-github-organization), users have two weeks to refute this revocation, if they wish by commenting on this pull-request and open a new pull-request to be re-added as approver after this one is merged.

Inactivity was detected by a github action, see #1443

Author: stephanme

toc/working-groups/app-runtime-interfaces.md

@@ -378,8 +378,6 @@ areas:
   - name: Ioannis Tsouvalas
     github: itsouvalas
   reviewers:
-  - name: Dennis Bell
-    github: dennisjbell
   - name: Tristan Poland
     github: tristanpoland
   - name: Jan Lucca Patzelt