feat: add additional step to "Administer subscriptions" onboarding flow

[kiram15]

Jira ticket

Testing instructions

• Navigate to a customer that has a license that can manage course requests (https://localhost.stage.edx.org:1991/HUSC/admin/subscriptions/manage-learners)
• Test the "Administer subscriptions" flow has 3 steps
• When you reach the end of the flow, the icon in the collapsible should turn black and show as completed

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

[codecov]

Codecov Report

❌ Patch coverage is 88.31169% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.91%. Comparing base (7a8d4f8) to head (dd3109b).

Files with missing lines	Patch %	Lines
src/components/ProductTours/TourCollapsible.tsx	86.20%	4 Missing ⚠️
...dingTours/data/useFetchCompletedOnboardingFlows.ts	81.81%	2 Missing ⚠️
...AdminOnboardingTours/flows/AdminOnboardingTour.tsx	75.00%	1 Missing ⚠️
...dminOnboardingTours/flows/CustomizeReportsFlow.tsx	66.66%	1 Missing ⚠️
...dminOnboardingTours/flows/SetUpPreferencesFlow.tsx	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1629      +/-   ##
==========================================
+ Coverage   86.88%   86.91%   +0.03%     
==========================================
  Files         780      781       +1     
  Lines       17694    17751      +57     
  Branches     3616     3707      +91     
==========================================
+ Hits        15374    15429      +55     
+ Misses       2253     2246       -7     
- Partials       67       76       +9     

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