[isort linter]: relax line length (88 instead of 79)
Summary:
Use the default line length for the isort linter, which is 88 with --profile=black
Scripted part of the diff: arc lint --everything
Depends on D13201
Test Plan: ninja check-functional-extended
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D13202