Remove requirement to add an API Secret for Pager Duty

[ThatGalNatalie]

PR Checklist:

• add a short description of what's changed to the top of the CHANGELOG.md
• add/update tests (or don't, for reasons explained below)

Describe this PR

• Removes check for apiToken in disableNext and allowSave
  Remove requirement to add an API Secret for Pager Duty actions #1051

[zhen0]

This looks @ThatGalNatalie

This isn't actually from your PR but in line https://github.com/PrefectHQ/ui/pull/1065/files#diff-3af46aeb97e3ab5dfecf9ff91442aa60a6bfd556c5f1b40ea61a760ffdfc3334R178

Could we add a check for apiToken?
E.g.

const whoTo = this.actionConfigArray.length
          ? this.actionConfigArray
          : this.secretName || this.webhookURLString || this.apiToken
          

Otherwise it shows null in the action name....

[zhen0]

LGTM @ThatGalNatalie