ref(less): Remove unused icon classes (#30709)

static/less/fonts.less

@@ -64,10 +64,6 @@
   -moz-osx-font-smoothing: grayscale;
 }
 
-.icon-support:before {
-  content: '\e910';
-}
-
 // Font based icons still in uses in Django rendered views.
 .icon-sentry-logo:before {
   content: '\e61a';
@@ -81,9 +77,6 @@
 .icon-arrow-left:before {
   content: '\e60e';
 }
-.icon-arrow-up:before {
-  content: '\e610';
-}
 .icon-arrow-right:before {
   content: '\e611';
 }