[mod] simple-theme: remove vendor CSS

flexbox
  Browser support for flexbox is excellent, and the majority of browsers do not
  need a prefix at this point. Safari was the last of the major browsers to
  remove prefixes, with the release of Safari 9 in 2015. [1]

user-select:
  Vendor prefix of user-select is not needed, see 'Browser compatibility' [2].

[1] https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Backwards_Compatibility_of_Flexbox#status_in_browsers
[2] https://developer.mozilla.org/en-US/docs/Web/CSS/user-select#browser_compatibility

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/static/themes/simple/src/less/mixins.less

@@ -1,6 +1,4 @@
-/*
-* SearXNG, A privacy-respecting, hackable metasearch engine
-*/
+// SPDX-License-Identifier: AGPL-3.0-or-later
 
 // Mixins
 .text-size-adjust (@property: 100%) {
@@ -25,44 +23,5 @@
 // disable user selection
 .disable-user-select () {
   -webkit-touch-callout: none;
-  -webkit-user-select: none;
-  -khtml-user-select: none;
-  -moz-user-select: none;
-  -ms-user-select: none;
   user-select: none;
 }
-
-// select all on focus
-.select-all-on-focus() {
-  -webkit-user-select: all;
-  -moz-user-select: all;
-  -ms-user-select: element;
-  user-select: all;
-}
-
-// see https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Advanced_layouts_with_flexbox
-.flexbox() {
-  display: -webkit-box;
-  display: -moz-box;
-  display: -webkit-flex;
-  display: -ms-flexbox;
-  display: flex;
-}
-
-.inline-flex() {
-  display: -webkit-inline-box;
-  display: -moz-inline-box;
-  display: -webkit-inline-flex;
-  display: -ms-inline-flexbox;
-  display: inline-flex;
-}
-
-.flex-direction-row() {
-  -webkit-box-direction: normal;
-  -webkit-box-orient: horizontal;
-  -moz-box-direction: normal;
-  -moz-box-orient: horizontal;
-  -webkit-flex-direction: row;
-  -ms-flex-direction: row;
-  flex-direction: row;
-}

searx/static/themes/simple/src/less/toolkit.less

@@ -99,7 +99,7 @@ tr {
   font-size: 0.8em;
   word-break: break-all;
   margin: 0.1em;
-  .select-all-on-focus();
+  user-select: all;
 }
 
 div.selectable_url {
@@ -218,8 +218,7 @@ div.selectable_url {
 }
 
 .tabs {
-  .flexbox();
-
+  display: flex;
   flex-wrap: wrap;
   width: 100%;
   min-width: 100%;