Bump mem and lerna-changelog

Removes [mem](https://github.com/sindresorhus/mem). It's no longer used after updating ancestor dependency [lerna-changelog](https://github.com/lerna/lerna-changelog). These dependencies need to be updated together.


Removes `mem`

Updates `lerna-changelog` from 0.8.3 to 2.2.0
- [Release notes](https://github.com/lerna/lerna-changelog/releases)
- [Changelog](https://github.com/lerna/lerna-changelog/blob/master/CHANGELOG.md)
- [Commits](lerna/lerna-changelog@v0.8.3...v2.2.0)

---
updated-dependencies:
- dependency-name: mem
  dependency-type: indirect
- dependency-name: lerna-changelog
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]