prevent running migration CI check if removal label is present

[cgoodfred]

Jira Ticket

COST-4947

Description

This change will allow skipping the migration check if we are removing fields from a model since the fields should be removed prior to the migration to drop those fields running.

Adding this allows us to follow along with the flow for removing fields suggested in this gist: https://gist.github.com/majackson/493c3d6d4476914ca9da63f84247407b#removing-fields-or-tables

Testing

1. This branch has run a few different times with and without the label with a model change. With the label the unit tests check runs smoothly and succeeds, without the label the unit tests fail similar to

Migrations for 'api':
  koku/api/migrations/0063_remove_providerinfrastructuremap_infrastructure_account_and_more.py
    - Remove field infrastructure_account from providerinfrastructuremap
    - Remove field infrastructure_region from providerinfrastructuremap
Migrations are out of sync with the models. Run 'make make-migrations' to update.

Release Notes

• proposed release note

* [COST-4947](https://issues.redhat.com/browse/COST-4947) Update CI check to allow removing model fields prior to migration

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.1%. Comparing base (91b0ffb) to head (5d38837).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5075     +/-   ##
=======================================
- Coverage   94.1%   94.1%   -0.0%     
=======================================
  Files        377     377             
  Lines      31346   31346             
  Branches    3715    3715             
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- Hits       29507   29503      -4     
- Misses      1173    1176      +3     
- Partials     666     667      +1