OLS4 case sensitivity

[sarahhunt]

Describe the bug

The previous implementation of extact matching in OLS was not case sensitive so, for example searching for 'Anterior Segment Dysgenesis' would return http://purl.obolibrary.org/obo/MONDO_0019503 - 'anterior segment dysgenesis'

In OLS 4 extact_match appears to be case sensitive, so searching for 'Anterior Segment Dysgenesis' returns nothing

To Reproduce

Compare examples: https://www.ebi.ac.uk/ols/search?q=Anterior+Segment+Dysgenesis&exact=on

https://www.ebi.ac.uk/ols4/search?q=Anterior+Segment+Dysgenesis&exactMatch=true

Expected behavior

Maintaining the previous behaviour would be more useful.