reword the text on the Centre Curation page

[bansp]

A minor thing, but worth taking a while: the current text at https://standards.clarin.eu/sis/views/list-curators.xq is not very clear -- let's have something clearer there...

[bansp]

Additionally, @margaretha suggested that, where the significance of colour-coding is mentioned, the relevant words should be colour-coded correspondingly (red, orange).

Also, since I don't want to create a merge conflict with Eliza's work, I will mark this issue as parent wrt the issue that Eliza is going to work on, i.e. column sorting (#506 ).