Remove unnecessary token_for from ChannelPointsReward.fetch_reward

[bartmoorman]

Description

The token_for argument of ChannelPointsReward.fetch_reward is unnecessary and results in a TypeError when not provided. This PR removes the unnecessary and unused argument.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
  • I have updated the changelog with a quick recap of my changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)
• I have read and agree to the Developer Certificate of Origin for this contribution