Remove protocol in Studio’s font URLs

Allow the fonts to be served using the same protocol as the current
page.

cms/static/sass/assets/_fonts.scss

@@ -7,37 +7,37 @@
   font-family: 'Open Sans';
   font-style: normal;
   font-weight: 700;
-  src: local('Open Sans Bold'), local('OpenSans-Bold'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/k3k702ZOKiLJc3WVjuplzKRDOzjiPcYnFooOUGCOsRk.woff) format('woff');
+  src: local('Open Sans Bold'), local('OpenSans-Bold'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/k3k702ZOKiLJc3WVjuplzKRDOzjiPcYnFooOUGCOsRk.woff) format('woff');
 }
 @font-face {
   font-family: 'Open Sans';
   font-style: normal;
   font-weight: 300;
-  src: local('Open Sans Light'), local('OpenSans-Light'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/DXI1ORHCpsQm3Vp6mXoaTaRDOzjiPcYnFooOUGCOsRk.woff) format('woff');
+  src: local('Open Sans Light'), local('OpenSans-Light'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/DXI1ORHCpsQm3Vp6mXoaTaRDOzjiPcYnFooOUGCOsRk.woff) format('woff');
 }
 @font-face {
   font-family: 'Open Sans';
   font-style: italic;
   font-weight: 700;
-  src: local('Open Sans Bold Italic'), local('OpenSans-BoldItalic'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/PRmiXeptR36kaC0GEAetxhbnBKKEOwRKgsHDreGcocg.woff) format('woff');
+  src: local('Open Sans Bold Italic'), local('OpenSans-BoldItalic'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/PRmiXeptR36kaC0GEAetxhbnBKKEOwRKgsHDreGcocg.woff) format('woff');
 }
 @font-face {
   font-family: 'Open Sans';
   font-style: italic;
   font-weight: 300;
-  src: local('Open Sans Light Italic'), local('OpenSansLight-Italic'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/PRmiXeptR36kaC0GEAetxvR_54zmj3SbGZQh3vCOwvY.woff) format('woff');
+  src: local('Open Sans Light Italic'), local('OpenSansLight-Italic'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/PRmiXeptR36kaC0GEAetxvR_54zmj3SbGZQh3vCOwvY.woff) format('woff');
 }
 @font-face {
   font-family: 'Open Sans';
   font-style: italic;
   font-weight: 400;
-  src: local('Open Sans Italic'), local('OpenSans-Italic'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/xjAJXh38I15wypJXxuGMBrrIa-7acMAeDBVuclsi6Gc.woff) format('woff');
+  src: local('Open Sans Italic'), local('OpenSans-Italic'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/xjAJXh38I15wypJXxuGMBrrIa-7acMAeDBVuclsi6Gc.woff) format('woff');
 }
 @font-face {
   font-family: 'Open Sans';
   font-style: normal;
   font-weight: 400;
-  src: local('Open Sans'), local('OpenSans'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/cJZKeOuBrn4kERxqtaUH3bO3LdcAZYWl9Si6vvxL-qU.woff) format('woff');
+  src: local('Open Sans'), local('OpenSans'), url(//themes.googleusercontent.com/static/fonts/opensans/v6/cJZKeOuBrn4kERxqtaUH3bO3LdcAZYWl9Si6vvxL-qU.woff) format('woff');
 }
 
 // Bree Serif - http://www.google.com/fonts/specimen/Bree+Serif
@@ -45,5 +45,5 @@
   font-family: 'Bree Serif';
   font-style: normal;
   font-weight: 400;
-  src: local('Bree Serif'), local('BreeSerif'), url(http://themes.googleusercontent.com/static/fonts/breeserif/v2/LQ7WLTaITDg4OSRuOZCps73hpw3pgy2gAi-Ip7WPMi0.woff) format('woff');
+  src: local('Bree Serif'), local('BreeSerif'), url(//themes.googleusercontent.com/static/fonts/breeserif/v2/LQ7WLTaITDg4OSRuOZCps73hpw3pgy2gAi-Ip7WPMi0.woff) format('woff');
 }