fix(workflow): update fig autocomplete workflow

[zwhitfield3]

Description

Work Item
Work Item

This PR updates the workflow for the Fig Autocomplete to get the latest config of the Heroku CLI in the form of a PR to Fig Autocomplete's repo when a new version of the Heroku CLI is released.

[zwhitfield3]

Some context for the updated acceptance test commit.

Due to the way Github workflows prevent yarn.locks from updating during execution, implementing the the fig spec required us to update our plugins property in the /packages/cli's package.json file. This now shows in our acceptance test which is why this commit exists.

[justinwilaby]

LGTM