Update all usages of 'control-label' with 'form-control-label' in docs

scss/_forms.scss

@@ -425,7 +425,7 @@ input[type="checkbox"] {
       width: 100%;
     }
 
-    .control-label {
+    .form-control-label {
       margin-bottom: 0;
       vertical-align: middle;
     }

scss/mixins/_forms.scss

@@ -6,7 +6,7 @@
 @mixin form-control-validation($color) {
   // Color the label and help text
   .help-block,
-  .control-label,
+  .form-control-label,
   .radio,
   .checkbox,
   .radio-inline,