When we merged TOR_RUST_VERSION from master, the allow_failures rule
did not match any more. Update it to make it match.
Closes 31859 for master.
## macOS rust and chutney are very slow, so we let the build finish before
## they are done. We'd like to fast finish, but still eventually show
## any failures in the build status. But Travis doesn't have that ability.
- - env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
+ - env: RUST_VERSION="nightly" RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
compiler: clang
os: osx
- env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"