Bump cross-spawn and gm (#476)

Bumps [cross-spawn](https://github.com/moxystudio/node-cross-spawn) and [gm](https://github.com/aheckmann/gm). These dependencies needed to be updated together.

Updates `cross-spawn` from 7.0.3 to 7.0.6
- [Changelog](https://github.com/moxystudio/node-cross-spawn/blob/master/CHANGELOG.md)
- [Commits](moxystudio/node-cross-spawn@v7.0.3...v7.0.6)

Updates `cross-spawn` from 6.0.5 to 7.0.6
- [Changelog](https://github.com/moxystudio/node-cross-spawn/blob/master/CHANGELOG.md)
- [Commits](moxystudio/node-cross-spawn@v7.0.3...v7.0.6)

Updates `gm` from 1.25.0 to 1.25.1
- [Changelog](https://github.com/aheckmann/gm/blob/master/History.md)
- [Commits](aheckmann/gm@1.25.0...1.25.1)

---
updated-dependencies:
- dependency-name: cross-spawn
  dependency-version: 7.0.6
  dependency-type: indirect
- dependency-name: cross-spawn
  dependency-version: 7.0.6
  dependency-type: indirect
- dependency-name: gm
  dependency-version: 1.25.1
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]