Remove the _font-url-prefixer function

This function was not actually being utilized and was likely an artifact from
refactoring the `font-face` mixin.

core/_bourbon.scss

@@ -12,7 +12,6 @@
 @import "bourbon/functions/contains";
 @import "bourbon/functions/contains-falsy";
 @import "bourbon/functions/font-source-declaration";
-@import "bourbon/functions/font-url-prefixer";
 @import "bourbon/functions/is-length";
 @import "bourbon/functions/is-light";
 @import "bourbon/functions/is-number";

core/bourbon/addons/_font-face.scss

@@ -36,8 +36,6 @@
 ///          format("truetype");
 ///   }
 ///
-/// @require {function} _font-url-prefixer
-///
 /// @require {function} _font-source-declaration
 ///
 /// @require {function} _bourbon-get-setting
@@ -49,16 +47,13 @@
     $file-formats: _bourbon-get-setting("global-font-file-formats")
   ) {
 
-  $font-url-prefix: _font-url-prefixer($asset-pipeline);
-
   @font-face {
     font-family: $font-family;
     src: _font-source-declaration(
       $font-family,
       $file-path,
       $asset-pipeline,
-      $file-formats,
-      $font-url-prefix
+      $file-formats
     );
     @content;
   }

core/bourbon/functions/_font-source-declaration.scss

@@ -2,8 +2,7 @@
   $font-family,
   $file-path,
   $asset-pipeline,
-  $file-formats,
-  $font-url) {
+  $file-formats) {
 
   $src: ();
 

spec/fixtures/functions/font-source-declaration.scss

@@ -1,10 +1,11 @@
 @import "setup";
-$file-formats: eot woff2 woff ttf svg;
+
+$file-formats: ("eot", "woff2", "woff", "ttf", "svg");
 
 .has-pipeline {
-  src: _font-source-declaration("a", "b", true, $file-formats, "/c");
+  src: _font-source-declaration("a", "b", true, $file-formats);
 }
 
 .no-pipeline {
-  src: _font-source-declaration("a", "b", false, $file-formats, "/c");
+  src: _font-source-declaration("a", "b", false, $file-formats);
 }