Remove font size option

GitHub uses different font sizes in different places so we can not put
them all under one variable without unexpectedly altering layout in some
places. If this is still desirable, it should be in a separate style.

github-dark.user.css

@@ -175,7 +175,6 @@
 }
 @advanced text font-choice "Code Font" Menlo
 @advanced text font-features "Code Font Features" normal
-@advanced text font-size-choice "Code Font Size" 12
 @advanced dropdown code-wrap "Code Wrap" {
   nowrap "No Wrap" <<<EOT
   EOT;
@@ -20188,7 +20187,6 @@
   #gist-form .file .input textarea, .blob-code-inner {
     font-family: "/*[[font-choice]]*/", Consolas, "Liberation Mono", Menlo, Courier, monospace !important;
     font-feature-settings: /*[[font-features]]*/ !important;
-    font-size: /*[[font-size-choice]]*/ !important;
   }
   /* Base link colors */
   .Header-link:focus, .Header-link:hover, table.files .octicon-file-directory,

index.html

@@ -1859,9 +1859,6 @@ <h3>CodeMirror Editor (JS)</h3>
   }, {
     pattern: '/*[[font-choice]]*/',
     replacement: config.font
-  }, {
-    pattern: '/*[[font-size-choice]]*/',
-    replacement: config.fontSize
   }, {
     pattern: '/*[[code-wrap]]*/',
     replacement: config.codeWrapCss

src/main.css

@@ -44,7 +44,6 @@
   #gist-form .file .input textarea, .blob-code-inner {
     font-family: "/*[[font-choice]]*/", Consolas, "Liberation Mono", Menlo, Courier, monospace !important;
     font-feature-settings: /*[[font-features]]*/ !important;
-    font-size: /*[[font-size-choice]]*/ !important;
   }
   /* Base link colors */
   .Header-link:focus, .Header-link:hover, table.files .octicon-file-directory,

src/template.css

@@ -64,7 +64,6 @@
 }
 @advanced text font-choice "Code Font" Menlo
 @advanced text font-features "Code Font Features" normal
-@advanced text font-size-choice "Code Font Size" 12
 @advanced dropdown code-wrap "Code Wrap" {
   nowrap "No Wrap" <<<EOT
   EOT;