Fixed wrong calculation of assigned components

[inietov]

Description

Components remaining are calculating just the rows of relation (table) components_assets, but every record on that table have a field called assigned_qty that needs to be added so the calculation of remaining components is correct.

Fixes freshdesk 29961

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Test Configuration:

• PHP version: 8.1
• MySQL version: 8.0.23
• Webserver version: nginx/1.19.8
• OS version: Debian 10

Checklist:

• I have read the Contributing documentation available here: https://snipe-it.readme.io/docs/contributing-overview
• I have formatted this PR according to the project guidelines: https://snipe-it.readme.io/docs/contributing-overview#pull-request-guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes