CI: Remove `-C debuginfo=0` from `RUSTFLAGS`
CI: Remove `-C debuginfo=0` from `RUSTFLAGS`

Having this flag is preventing tarpaulin from providing us with test coverage reports and I can't find any documented reason for why we would need this.

rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io