Make sure tutorial categories are case-insensitive

[nottrobin]

See detail here: https://github.com/canonical-web-and-design/web-squad/issues/4907#issuecomment-1073876325

[petesfrench]

I was unable to find the tutorial mentioned in the original issue and using upper and lower case letters did not change my results. I did however get different results by using a hyphen in multi-pass. So we should account for this also.