chore(deps): bump mem and nyc

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


Removes `mem`

Updates `nyc` from 11.9.0 to 15.1.0
- [Release notes](https://github.com/istanbuljs/nyc/releases)
- [Changelog](https://github.com/istanbuljs/nyc/blob/master/CHANGELOG.md)
- [Commits](istanbuljs/nyc@v11.9.0...v15.1.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]