[PM-27179] Fix Admin portal user view to only show individual item count

[r-tome]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-27179

📔 Objective

Fixes the Items count in Admin Portal's user view to display only individually-owned items.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Protected functional changes with optionality (feature flags)
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation (Confluence, contributing docs) or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[github-actions]

Checkmarx One – Scan Summary & Details – f92911d7-a94d-4d6d-abdf-487e9abfda96

Great job! No new security vulnerabilities introduced in this pull request

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 56.06%. Comparing base (b360d6a) to head (24c28a5).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Admin/Controllers/UsersController.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6888      +/-   ##
==========================================
- Coverage   59.97%   56.06%   -3.92%     
==========================================
  Files        1967     1967              
  Lines       86902    86902              
  Branches     7737     7737              
==========================================
- Hits        52122    48718    -3404     
- Misses      32896    36384    +3488     
+ Partials     1884     1800      -84     

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