fix: Agent count not updating after removing agents (#29871)

apps/meteor/app/livechat/server/api/lib/users.ts

apps/meteor/app/livechat/server/hooks/afterAgentRemoved.ts

apps/meteor/app/livechat/server/index.ts

apps/meteor/app/livechat/server/lib/Livechat.js

...t/views/omnichannel/agents/AgentsTable/AgentsTableRow.tsx

...iews/omnichannel/agents/AgentsTable/RemoveAgentButton.tsx

apps/meteor/lib/callbacks.ts

apps/meteor/server/models/raw/LivechatDepartment.ts

apps/meteor/server/models/raw/Users.js

...ages/model-typings/src/models/ILivechatDepartmentModel.ts

packages/model-typings/src/models/IUsersModel.ts

packages/rest-typings/src/v1/omnichannel.ts