Fix prettier version to 3.0.0

[danielpeintner]

Shall we do the same as in w3c/wot-thing-description#2152 given that w3c/wot-binding-templates#444 showed some issues with another prettier version ...

[danielpeintner]

see findings in w3c/wot-binding-templates#444 (comment)

[danielpeintner]

Strangely enough, in the node-wot case we should not change the prettier version to 3.0.0 given it causes issues
see #1447