Use inline code for varaiables in harbor text

What does this MR do and why?

Related to #375990 (closed)

I spun this out of !98902 (comment 1116488686)

Display the Harbor variables as inline code, makes those variables stand out just a little bit better.

normal text	inline code

How to set up and validate locally

1. Go to the Harbor integration page of a project, such as http://ee.gitlab.test:5100/flightjs/Flight/-/settings/integrations/harbor/edit
2. See that the variables such as $HARBOR_HOST in the help text are displayed as inline code.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.