[FIX] web: restore CSS kanban AttachmentImage field

Modification in 60aa9ffd of web module kanban_view.scss contained
unused CSS style and style that affected usage of AttachmendImage field
in a normal kanban view.

The correct code was added in commit 6e12372f in composer.scss of mail
module.

opw-1892053
closes #27923

addons/web/static/src/scss/kanban_view.scss

@@ -283,20 +283,8 @@
         }
 
         .o_attachment_image > img {
-            overflow: hidden;
-            padding-top: 75%;
-
-            .o_attachment_image {
-                @include o-position-absolute(0, 0, 0, 0);
-                background-size: cover;
-                background-position: center;
-                transform: scale(1.05);
-                transition: all 0.3s;
-            }
-
-            &:hover .o_attachment_image {
-                transform: scale(1);
-            }
+            width: 100%;
+            height: auto;
         }
 
         .o_progressbar {