Upgrade acts-on-taggable to v7.0.0
This eliminates the Ruby 2.7 kwargs warning and adds support for Rails 6.1.
CHANGELOG: https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md
Diff: https://github.com/mbleigh/acts-as-taggable-on/compare/v6.5.0..v7.0.0
Edited by Stan Hu