Fixed inconsistency in --html-app FILE in cli-reference

[maynaS]

Fixes #2789

Before

scancode -clpieu --csv output.html samples

After

scancode -clpieu --html-app output.html samples

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📑 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR
  Run tests locally to check for errors.
• Commits are in uniquely-named feature branch and has no merge conflicts 📁
  It is a small documentation change, therefore I pushed it to the develop branch itself.

[pombredanne]

@maynaS Thank you ++
You need to format you signoff, it must be on the last line of your commit message.
Also do you mind to squash all in a single clean commit with a single clean message?

[pombredanne]

Thanks! Do you mind to squash your commits in a single one with
A subject that's less than 50 characters
A signoff on the last line of the message

[maynaS]

@pombredanne Hey, can you check it out? I have done what you asked for

[pombredanne]

Thank you ++
LGTM, merging!