Consistent brand fonts

We use the standard system fonts by default everywhere. The CSS rule was copied 1:1 from the Nextcloud server repository.

Signed-off-by: Iva Horn <iva.horn@nextcloud.com>

static/css/styles.css

@@ -1,40 +1,6 @@
 
 /*---- General ----*/
 
-/* enable to reveal boxes everywhere  */
-/** {
-    border-style: solid;
-    border-color: red;
- }*/
-
-@font-face {
-    font-family: 'Open Sans';
-    font-style: normal;
-    font-weight: normal;
-    src: local('Open Sans'), local('OpenSans'), url(fonts/OpenSans-Regular.woff) format('woff'), url(fonts/OpenSans-Regular.ttf) format('ttf');
-}
-
-@font-face {
-    font-family: 'Open Sans';
-    font-style: normal;
-    font-weight: bold;
-    src: local('Open Sans Semibold'), local('OpenSans-Semibold'), url(fonts/OpenSans-Semibold.woff) format('woff'), url(fonts/OpenSans-Semibold.ttf) format('ttf');
-}
-
-@font-face {
-    font-family: 'Open Sans';
-    font-style: italic;
-    font-weight: normal;
-    src: local('Open Sans Italic'), local('OpenSans-Italic'), url(fonts/OpenSans-Italic.woff) format('woff'), url(fonts/OpenSans-Bold.ttf) format('ttf');
-}
-
-@font-face {
-    font-family: 'Open Sans';
-    font-style: normal;
-    font-weight: light;
-    src: local('Open Sans Light'), local('OpenSans-Light'), url(fonts/OpenSans-Light.woff) format('woff'), url(fonts/OpenSans-Light.ttf) format('ttf');
-}
-
 @font-face {
   font-family: 'Glyphicons Halflings';
 
@@ -54,7 +20,7 @@ span.avoidwrap {
 
 /* Make background white, font grey and default buttons a bit darker to compensate */
 body {
-    font-family: 'Open Sans', Frutiger, Calibri, 'Myriad Pro', Myriad, sans-serif !important;
+    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Oxygen-Sans, Cantarell, Ubuntu, "Helvetica Neue", "Noto Sans", "Liberation Sans", Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
     color: #555;
     background: #fff;
 }