Fix incorrect generator start report

Current situation

launchGenerator is a generator job, not a function:

$ opentf-ctl get workflow 2b1
Workflow Workflow end-to-end TestSuite af7a26df-d3c5-4e92-b4f2-1d1d9bd316bd
(running in namespace 'default')
[2024-07-26T09:35:45] [job 3453121c-ab66-4cf9-a0a2-b9a77f04608a] Running function launchGenerator
[2024-07-26T09:35:46] [job f42e1144-4eb8-47eb-9ed9-bdc8749547f9] Requesting execution environment providing ['linux', 'postman'] in namespace 'default' for job 'squashTMJob-0'