I'm not really sure where this crept in (quite a while ago by the looks of it), but we should be following the standard js rules for quotes: https://github.com/standard/eslint-config-standard/blob/bcd019906cd379be04ef8e6347e108bad4fc448d/.eslintrc.json#L201
..so using backtick quotes should be allowed if there is a variable substitution but not otherwise. i.e:
I guess some other plugin we are using is overriding the rule. Not 100% sure.
Anyway, this PR explicitly re-enables the rule in our eslint config and re-formats all the places where we are using backtick strings with no templating. In general, I don't like to spend a lot of time bikeshedding lint config but I think this is an improvement.