stop building docs on each CI run

.gitlab-ci.yml

@@ -3,7 +3,6 @@ image: bitsmart/rust:1.32
 stages:
   - lint
   - build
-  - doc
 
 lint:
   stage: lint
@@ -38,19 +37,3 @@ test:
   script:
     - cargo test --features backend_piston,backend_gilrs
 
-doc:
-  stage: doc
-  cache:
-    key: artifacts
-    paths:
-      - target
-      - Cargo.lock
-    policy: pull
-  script:
-    - cargo doc --features backend_piston,backend_gilrs
-    - mv target/doc/prongs/ public/
-  artifacts:
-    paths:
-      - public
-  only:
-    - master