Bump rustup from 1249d1e to 7ebe42b

Bumps [rustup](https://github.com/rust-lang-nursery/rustup.rs) from `1249d1e` to `7ebe42b`.
- [Release notes](https://github.com/rust-lang-nursery/rustup.rs/releases)
- [Commits](rust-lang/rustup@1249d1e...7ebe42b)

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

Author: dependabot-preview[bot]