Fixes some less compilation problems in Magento's luma theme.

Author: hostep

app/design/frontend/Magento/luma/Magento_Checkout/web/css/source/module/checkout/_estimated-total.less

@@ -14,7 +14,6 @@
     //  ---------------------------------------------
 
     .opc-estimated-wrapper {
-        &:extend(.abs-no-display-desktop all);
         &:extend(.abs-add-clearfix all);
         .lib-css(background, @checkout-step-content-mobile__background);
         .lib-css(border-bottom, @checkout-step-title__border);
@@ -54,6 +53,6 @@
 
 .media-width(@extremum, @break) when (@extremum = 'min') and (@break = @screen__m) {
     .opc-estimated-wrapper {
-        display: none;
+        &:extend(.abs-no-display-desktop all);
     }
 }

app/design/frontend/Magento/luma/Magento_Checkout/web/css/source/module/checkout/fields/_file-uploader.less

@@ -129,7 +129,6 @@
 
 .file-uploader-preview {
     .action-remove {
-        &:extend(.abs-action-reset all);
         .lib-icon-font (
                 @icon-delete__content,
             @_icon-font: @icons__font-name,

app/design/frontend/Magento/luma/Magento_Downloadable/web/css/source/_module.less

@@ -92,7 +92,6 @@
         }
 
         .field.choice {
-            &:extend(.clearer all);
             border-bottom: 1px solid @color-gray92;
             box-sizing: border-box;
             margin-bottom: @indent__s;
@@ -178,10 +177,6 @@
 
 .media-width(@extremum, @break) when (@extremum = 'min') and (@break = @screen__m) {
     .page-product-downloadable {
-        .product-add-form {
-            &:extend(.clearer all);
-        }
-
         .product-options-wrapper {
             float: left;
             width: 55%;

app/design/frontend/Magento/luma/Magento_GiftMessage/web/css/source/_module.less

@@ -27,7 +27,6 @@
 & when (@media-common = true) {
     .gift-message {
         .field {
-            &:extend(.abs-clearfix all);
             margin-bottom: @indent__base;
 
             .label {