Update github action for cluster-api-installer to match new ranch names

the github action must be updated to reflect the new branches backplane-2.8, backplane-2.9 & backplane-2.10 with each branch target release for CAPI & CAPI providers

https://github.com/stolostron/cluster-api-installer/blob/main/.github/workflows/crons.yml

Definition of Done for Engineering Story Owner (Checklist)

• ...

Development Complete

• The code is complete.
• Functionality is working.
• Any required downstream Docker file changes are made.

Tests Automated

• [ ] Unit/function tests have been automated and incorporated into the
  build.
• [ ] 100% automated unit/function test coverage for new or changed APIs.

Secure Design

• [ ] Security has been assessed and incorporated into your threat model.

Multidisciplinary Teams Readiness

• [ ] Create an informative documentation issue using the Customer

Portal Doc template that you can access from [The Playbook](

https://docs.google.com/document/d/1YTqpZRH54Bnn4WJ2nZmjaCoiRtqmrc2w6DdQxe_yLZ8/edit#heading=h.9fvyr2rdriby),

and ensure doc acceptance criteria is met.

• Call out this sentence as it's own action:

• [ ] Link the development issue to the doc issue.

Support Readiness

• [ ] The must-gather script has been updated.