use stable rust toolchain in ci

cumulus/.gitlab-ci.yml

@@ -109,8 +109,6 @@ variables:
     - !reference [.common-before-script, before_script]
     - rustup show
     - cargo --version
-    - rustup +nightly show
-    - cargo +nightly --version
     - bash --version
   tags:
     - linux-docker-vm-c2

cumulus/scripts/ci/gitlab/pipeline/build.yml

@@ -40,7 +40,7 @@ build-test-parachain:
       artifacts: false
   script:
     - echo "___Building a binary, please refrain from using it in production since it goes with the debug assertions.___"
-    - time cargo +nightly build --release --locked --bin test-parachain
+    - time cargo build --release --locked --bin test-parachain
     - echo "___Packing the artifacts___"
     - mkdir -p ./artifacts
     - mv ./target/release/test-parachain ./artifacts/.

cumulus/scripts/ci/gitlab/pipeline/test.yml

@@ -84,7 +84,7 @@ check-rustdoc:
     SKIP_WASM_BUILD: 1
     RUSTDOCFLAGS: "-Dwarnings"
   script:
-    - time cargo +nightly doc --workspace --all-features --verbose --no-deps
+    - time cargo doc --workspace --all-features --verbose --no-deps
 
 cargo-check-benches:
   stage: test