Don't allow nightly runs to fail

rust-bindings/rust/.gitlab-ci.yml

@@ -23,7 +23,6 @@ ostree-sys_nightly:
   image: rustlang/rust:nightly
   script:
   - cargo test --verbose --manifest-path sys/Cargo.toml --features "v2018_9" #--all-features
-  allow_failure: true
 
 publish_ostree-sys:
   stage: publish
@@ -42,7 +41,6 @@ ostree_nightly:
   image: rustlang/rust:nightly
   script:
   - cargo test --verbose --features "v2018_9" #--all-features
-  allow_failure: true
 
 publish_ostree:
   stage: publish