Update Markdown guidelines: links
Sid asked us to change the current guidelines on writing links in markdown to inline links:
[text](http://link.com)
I'm gonna change it here https://about.gitlab.com/handbook/marketing/developer-relations/technical-writing/markdown-guide/#links
Ref: 2c050a79 (comment 23698638)
cc/ @sytses @kirstenabma FYI :)