Remove `cursor: pointer` from everything accept links

[chris-pearce]

Basically keep it at the correct user-agent styles.

Related styles:

• https://github.com/campaignmonitor/shell/blob/master/src/_normalise-reset.scss#L449
• https://github.com/campaignmonitor/shell/blob/master/src/_normalise-reset.scss#L478-L487

Further reading.