Update revenue figure on homepage

This updates the number to be the same as it currently is on
coops.tech. There's a separate
issue (https://git.coop/cotech/website/issues/29) to populate this
from the YAML front matter in each file under `_coops`.

index.html

@@ -20,7 +20,7 @@ layout: home
       <div class="small-3 columns">
         <img src="/app/themes/coop-tech-oowp-theme/public/img/icon-revenue.png" class="float-center">
         <h6>Revenue</h6>
-        <h5>£5.7m</h5>
+        <h5>£10.3m</h5>
       </div>
       <div class="small-3 columns">
         <img src="/app/themes/coop-tech-oowp-theme/public/img/icon-clients.png" class="float-center">