Remove unused file and CSS selectors

[janfaracik]

ClickHandler.js is no longer used/nor loaded anywhere, nor are the related CSS selectors. Was previously used in #169 but the method of copying URLs was replaced in #222.

Testing done

• Plugin works as before

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[MarkEWaite]

Thanks! I interactively tested the copy and paste and the presentation with the default theme and with the dark theme. It worked as expected with my Jenkins controller over https.