[FIX] web_editor: fix gradient slider infinite resize and safari support

Prior to this commit, if three colors were selected for a gradient and
the user would click on the third color, if that color had a value of
100%, in some conditions the picker would resize infinitely.
Also prior to this commit, the color picker slider was not supported
well under safari.

This commit fixes the SCSS rules in order to fix those behaviours.

task-2670809

X-original-commit: 5a91d8b00c35cb597b0ee5f5ec8605e4589f81c9
Part-of: odoo/odoo#80466

addons/web_editor/static/src/scss/wysiwyg_snippets.scss

@@ -1823,7 +1823,7 @@ body.editor_enable.editor_has_snippets {
                     grid-column: 1/span 2;
                     grid-row: 3;
                     background: none;
-                    -webkit-appearance: none;
+                    appearance: none;
                     cursor: ew-resize;
                     @supports (-moz-appearance:none) {
                         margin-top: 2px;
@@ -1833,7 +1833,7 @@ body.editor_enable.editor_has_snippets {
                         pointer-events: auto;
                         border: 1.5px solid rgba(255, 255, 255, 0.8);
                         background: currentColor;
-                        -webkit-appearance: none;
+                        appearance: none;
                         box-shadow: 0px 0px 0px #000000;
                         height: 20px;
                         width: 12px;
@@ -1877,6 +1877,7 @@ body.editor_enable.editor_has_snippets {
             .o_remove_color {
                 font-size: 14px !important;
                 text-align: center !important;
+                padding: 0;
             }
         }
     }