UI enhancements on mobile (#6180)

* Set fallback font for log viewer

* Enable logo scaling in About view

* Don't split "dependency list" into 2 columns on mobile

gui/default/syncthing/core/aboutModalView.html

@@ -1,7 +1,7 @@
 <modal id="about" status="info" icon="far fa-heart" heading="{{'About' | translate}}" large="yes" closeable="yes">
   <div class="modal-body">
     <h1 class="text-center">
-      <img alt="Syncthing" src="assets/img/logo-horizontal.svg" style="vertical-align: -16px" height="100" width="366" />
+      <img alt="Syncthing" src="assets/img/logo-horizontal.svg" style="max-width: 366px; vertical-align: -16px" />
       <br />
       <small>{{versionString()}}</small>
       <br />