Bump sinatra from `4ceed83` to `6f15fba`
Bump sinatra from `4ceed83` to `6f15fba`

Bumps [sinatra](https://github.com/sinatra/sinatra) from `4ceed83` to `6f15fba`.
- [Release notes](https://github.com/sinatra/sinatra/releases)
- [Commits](https://github.com/sinatra/sinatra/compare/4ceed83a16ea3f3b018d11004079393baa5c5200...6f15fba2790ebdf4d1215cebf425dea2ea3130ea)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
dwilkie/twilreapi,dwilkie/twilreapi