Remove unused radio and checkbox styles

The styles for custom radio buttons and checkboxes should be used
instead.

These can be found in forms/_form-block-labels.scss

public/sass/elements/_forms.scss

@@ -169,28 +169,6 @@ textarea.form-control {
 }
 // scss-lint:enable QualifyingElement
 
-// Radio buttons
-.form-radio {
-  display: block;
-  margin: 10px 0;
-
-  input {
-    vertical-align: middle;
-    margin: -4px 5px 0 0;
-  }
-}
-
-// Checkboxes
-.form-checkbox {
-  display: block;
-  margin: $gutter-half 0;
-
-  input {
-    vertical-align: middle;
-    margin: -2px 5px 0 0;
-  }
-}
-
 
 // 6. Form control widths
 // ==========================================================================