chore(deps): bump @typespec/rest from 0.75.0 to 0.78.0 in /additions

Bumps [@typespec/rest](https://github.com/microsoft/typespec) from 0.75.0 to 0.78.0.
- [Release notes](https://github.com/microsoft/typespec/releases)
- [Commits](https://github.com/microsoft/typespec/compare/@typespec/rest@0.75.0...@typespec/rest@0.78.0)

---
updated-dependencies:
- dependency-name: "@typespec/rest"
  dependency-version: 0.78.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]