Bump reqwest from 0.12.12 to 0.12.15

Bumps [reqwest](https://github.com/seanmonstar/reqwest) from 0.12.12 to 0.12.15.
- [Release notes](https://github.com/seanmonstar/reqwest/releases)
- [Changelog](https://github.com/seanmonstar/reqwest/blob/master/CHANGELOG.md)
- [Commits](seanmonstar/reqwest@v0.12.12...v0.12.15)

---
updated-dependencies:
- dependency-name: reqwest
  dependency-version: 0.12.15
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]