feat: add removed members count

[katrinan029]

Description

Adds the removed learners count to toggle in the Members tab when there are removed members.
https://2u-internal.atlassian.net/browse/ENT-8968

UI Updates

figma	before	after

Test plan

1. checkout branch knguyen2/ent-8968. in your terminal, run the follow commands:
   • git fetch
   • git checkout knguyen2/ent-8968
   • npm run start:stage
2. use staging link https://localhost.stage.edx.org:1991/exec-ed-2u-integration-qa/admin/learner-credit/92fa52bc-6863-49ff-8a32-1cfefbfbb728/members to verify that the count of removed learners is in the toggle
3. confirm that when toggled is on, the removed learner should appear in the data table
   
4. verify changes match figma mocks
   https://www.figma.com/design/H69Met5YL7xu5w5LRliumQ/Groups-MVP?node-id=4289-23202&t=0DKGA6qrlzZz0EyD-0

For all changes

• Ensure adequate tests are in place (or reviewed existing tests cover changes)

Only if submitting a visual change

• Ensure to attach screenshots
• Ensure to have UX team confirm screenshots

[kiram15]

Looks great!

[codecov]

Codecov Report

Attention: Patch coverage is 35.89744% with 25 lines in your changes are missing coverage. Please review.

Project coverage is 85.26%. Comparing base (4861bd3) to head (dcd9c5d).

Files	Patch %	Lines
...ent/data/hooks/useEnterpriseRemovedGroupMembers.js	4.16%	20 Missing and 3 partials ⚠️
...ent/members-tab/BudgetDetailMembersTabContents.jsx	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1234      +/-   ##
==========================================
- Coverage   85.43%   85.26%   -0.18%     
==========================================
  Files         537      538       +1     
  Lines       11739    11773      +34     
  Branches     2495     2497       +2     
==========================================
+ Hits        10029    10038       +9     
- Misses       1657     1678      +21     
- Partials       53       57       +4     

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