Remove: machine_accounts feature flag.

[Mujib-Ahasan]

Summary

The default value of machine_accounts flag is false now. But related functionalities sets it to true. This PR is raised for the release of the flag.

Fixes #5435

[evankanderson]

The test failure appears to be valid:

❌ TestAssignRole/grant_permission_to_GitHub_Action (0s)
      handlers_authz_test.go:894: 
          	Error Trace:	/home/runner/work/minder/minder/internal/controlplane/handlers_authz_test.go:894
          	Error:      	Received unexpected error:
          	            	Code: 12
          	            	Name: UNIMPLEMENTED
          	            	Description: Unimplemented
          	            	Details: machine accounts are not enabled
          	Test:       	TestAssignRole/grant_permission_to_GitHub_Action
      controller.go:251: missing call(s) to *mock_roles.MockRoleService.CreateRoleAssignment(is anything, is anything, is anything, is anything, is equal to {repo:mindersec/community:ref:refs/heads/main  githubactions  } (auth.Identity), is equal to admin (authz.Role)) /home/runner/work/minder/minder/internal/controlplane/handlers_authz_test.go:839
      controller.go:251: aborting test due to missing call(s)

[evankanderson]

Ooh, this is tricky, since this is a negative use of the flag -- in this case, I think flags.Bool(ctx, s.featureFlags, flags.MachineAccounts) should effectively always return true, so if isMachine && !true will always evaluate to false, and the entire if false {...} block can be removed.

[github-actions]

This PR needs additional information before we can continue. It is now marked as stale because it has been open for 30 days with no activity. Please provide the necessary details to continue or it will be closed in 30 days.

[evankanderson]

I think the test failure here is clear and fairly simple (the wrong flag branch was removed).

[github-actions]

This PR needs additional information before we can continue. It is now marked as stale because it has been open for 30 days with no activity. Please provide the necessary details to continue or it will be closed in 30 days.