Merge branch 'patch-1' into 'master'

Update .gitlab-ci.yml

See merge request cocsn/gosdn!58

.gitlab-ci.yml

@@ -62,7 +62,7 @@ documentation:pdf:
   before_script:
       - cargo install mdbook
   image:
-    name: rustdocker/rust:stable
+    name: rust:latest
   stage: documentation
   script:
   - mdbook build documentation --dest-dir public