Remove smooth scroll behaviour

It's not adapted to a SPA because the scroll is updated when we change page

client/src/sass/application.scss

@@ -18,10 +18,6 @@ $assets-path: '../../assets/';
   display: none !important;
 }
 
-html {
-  scroll-behavior: smooth;
-}
-
 body {
   /*** theme ***/
   // now beware node-sass requires interpolation