Cleanup comments and docs in channel fee update logic#1047

Merged

TheBlueMatt merged 2 commits intolightningdevkit:mainfrom

TheBlueMatt:2021-08-985-followups

Sep 9, 2021

Commits on Sep 9, 2021

Update docs for pending_update_fee and holding_cell_update_fee
TheBlueMatt
committed
Add further comments around fee update handling in channel
TheBlueMatt
committed