Bump gulp-sourcemaps from 2.6.5 to 3.0.0

Bumps [gulp-sourcemaps](https://github.com/gulp-sourcemaps/gulp-sourcemaps) from 2.6.5 to 3.0.0.
- [Release notes](https://github.com/gulp-sourcemaps/gulp-sourcemaps/releases)
- [Commits](gulp-sourcemaps/gulp-sourcemaps@v2.6.5...v3.0.0)

---
updated-dependencies:
- dependency-name: gulp-sourcemaps
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]