Improve p.field-css-classes.description usability: switch to .description-wide

From: Leho Kraav <leho@kraav.com>

Menu item CSS class editor field is super narrow, for no obvious reason. For
any class attribute list longer than a single element, this .description-thin
control is just plain uncomfortable to use.

.description-wide expands the field to 100% width and all is good.
---
 wp-admin/includes/class-walker-nav-menu-edit.php   |    2 +-
 .../class-wp-customize-nav-menu-item-control.php   |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/wp-admin/includes/class-walker-nav-menu-edit.php b/wp-admin/includes/class-walker-nav-menu-edit.php
index b13e9d8..eb2e9c9 100644
--- a/wp-admin/includes/class-walker-nav-menu-edit.php
+++ b/wp-admin/includes/class-walker-nav-menu-edit.php
@@ -177,7 +177,7 @@ class Walker_Nav_Menu_Edit extends Walker_Nav_Menu {
 						<?php _e( 'Open link in a new tab' ); ?>
 					</label>
 				</p>
-				<p class="field-css-classes description description-thin">
+				<p class="field-css-classes description description-wide">
 					<label for="edit-menu-item-classes-<?php echo $item_id; ?>">
 						<?php _e( 'CSS Classes (optional)' ); ?><br />
 						<input type="text" id="edit-menu-item-classes-<?php echo $item_id; ?>" class="widefat code edit-menu-item-classes" name="menu-item-classes[<?php echo $item_id; ?>]" value="<?php echo esc_attr( implode(' ', $item->classes ) ); ?>" />
diff --git a/wp-includes/customize/class-wp-customize-nav-menu-item-control.php b/wp-includes/customize/class-wp-customize-nav-menu-item-control.php
index 466f214..4fa22fa 100644
--- a/wp-includes/customize/class-wp-customize-nav-menu-item-control.php
+++ b/wp-includes/customize/class-wp-customize-nav-menu-item-control.php
@@ -111,7 +111,7 @@ class WP_Customize_Nav_Menu_Item_Control extends WP_Customize_Control {
 					<input type="text" id="edit-menu-item-attr-title-{{ data.menu_item_id }}" class="widefat edit-menu-item-attr-title" name="menu-item-attr-title" />
 				</label>
 			</p>
-			<p class="field-css-classes description description-thin">
+			<p class="field-css-classes description description-wide">
 				<label for="edit-menu-item-classes-{{ data.menu_item_id }}">
 					<?php _e( 'CSS Classes' ); ?><br />
 					<input type="text" id="edit-menu-item-classes-{{ data.menu_item_id }}" class="widefat code edit-menu-item-classes" name="menu-item-classes" />