fix(CSS): correct button font

* (FIX) SURF-951: Button implementation off spec

Author: Ryan A. Johnson

src/helix-ui/styles/modules/button.less

@@ -4,6 +4,7 @@
   border: 1px solid @cyan-900;
   color: @cyan-900;
   cursor: pointer;
+  font: inherit;
   font-size: 0.875rem;
   font-weight: 500;
   line-height: 1;