Make fallback font 'serif', rather than 'sans-serif' fonts

Author: cllns

src/doc/rust.css

@@ -58,7 +58,7 @@
 body {
     margin: 0 auto;
     padding: 0 15px;
-    font-family: "Source Serif Pro", "Helvetica Neue", Helvetica, Arial, sans-serif;
+    font-family: "Source Serif Pro", Georgia, Times, "Times New Roman", serif;
     font-size: 18px;
     color: #333;
     line-height: 1.428571429;

src/librustdoc/html/static/main.css

@@ -64,7 +64,7 @@
 
 body {
     color: #333;
-    font: 16px/1.4 "Source Serif Pro", "Helvetica Neue", Helvetica, Arial, sans-serif;
+    font: 16px/1.4 "Source Serif Pro", Georgia, Times, "Times New Roman", serif;
     margin: 0;
     position: relative;
     padding: 10px 15px 20px 15px;