Documentation search: tweak search term highlight design

Follow-up to #6833 from Tom: https://github.com/wagtail/wagtail/pull/6833#issuecomment-786558723:

I dislike the standard RTD search term highlighting, and I usually remove the ?highlight=video param before sharing search results, e.g. in responses to support questions on Slack. I’d be in favour of removing that styling here - what do others think?

Here is the code that handles this. I think removing the highlight would just be a matter of removing this code: https://github.com/wagtail/wagtail/blob/23f146c7e115fc1daa342b6084ee94531cbe44dd/docs/_templates/search.html#L61-L64

[tomdyson]

Can we vote on this comment to gauge opinion?

👍🏼 = ‘we should keep highlighting’ 👎🏼 = ‘we should remove highlighting’

[Scotchester]

I think the feature is worth retaining. My query for Tom was whether less-jarring highlighting would appease his original concern. From his reply to this issue, it seems like it would.

I think you’re right, Thibaud, that it should be jarring enough not to be confused with regular formatting – I’m not sure just bolding would suffice – but whatever we land on, it does still need to meet minimum color contrast requirements.