Update volunteer testimonials

[antoinepetty]

We had some different ones from the competition booklet for SR2022, could add them to the site

[sedders123]

The testimonials from the booklet are from myself, Becky and Peter. Peter's came from the website and both myself and Becky already have testimonials on the home page. Feels like it would be good to showcase different volunteers if we are going to refresh these.