Added missing font import to admin-lte.scss

Updated admin-lte.scss with the missing font import.

Author: Jearnest94

app/assets/adminlte/admin-lte.scss

@@ -7,4 +7,5 @@ $fa-font-path: "~@fortawesome/fontawesome-free/webfonts/";
 @import '~@fortawesome/fontawesome-free/scss/solid';
 @import '~@fortawesome/fontawesome-free/scss/brands';
 @import '~daterangepicker/daterangepicker.css';
-@import '~bootstrap-select/dist/css/bootstrap-select.min.css';
+@import '~bootstrap-select/dist/css/bootstrap-select.min.css';
+@import url(https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,600,700,300italic,400italic,600italic);