Revert "Fixed keyboard focus remains within modal simulated dialogs."

This reverts commit 3c84b7a1.

lms/static/sass/partials/base/_variables.scss

@@ -372,7 +372,7 @@ $body-line-height: golden-ratio(.875em, 1) !default;
 $base-font-color: rgb(60,60,60) !default;
 $baseFontColor: $base-font-color;
 
-$lighter-base-font-color: rgb(100,100,100) !default;
+$lighter-base-font-color: rgb(100,100,100) $base-font-color;
 $very-light-text: rgb(255,255,255) !default;
 $text-color: rgb(51, 51, 51) !default;