Disable the line length limit for Markdown syntax check job

Since we're not working on teletypes anymore, I think the 80 character line limit in Markdown is not really necessary.

.gitlab-industrial-ci-kinetic-with-rosinstall.yml

@@ -53,10 +53,13 @@ bash_syntax:
 ##########################################################
 ## Check for errors in markdown files
 ## Uses https://github.com/cytopia/awesome-ci
+## Disables the line length rule with --custom="-r ..."
+## See other rules that can be configured in
+## https://github.com/markdownlint/markdownlint/blob/master/docs/RULES.md
 ##########################################################
 markdown_syntax:
   stage: postcheck
-  script: docker run -v ${PWD}:/ac cytopia/awesome-ci syntax-markdown --path=/ac --extension=md --ignore=.ci_config
+  script: docker run -v ${PWD}:/ac cytopia/awesome-ci syntax-markdown --path=/ac --extension=md --ignore=.ci_config --custom="-r ~MD013"
   allow_failure: yes
   when: always