[REF] web: BS4, review kanban design

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

@@ -453,14 +453,9 @@
                 }
 
                 input, input:focus, input:hover {
-                    margin-top: 3px;
                     font-size: 16px;
                     background: transparent;
                 }
-
-                .o_kanban_add {
-                    margin-left: 10px;
-                }
             }
 
             .o_kanban_muted_record {

addons/web/static/src/xml/kanban.xml

@@ -51,7 +51,7 @@
         <div class="o_quick_create_unfolded">
             <div class="o_kanban_header">
                 <div class="input-group">
-                    <input type="text" class="o_input" placeholder="Column title"/>
+                    <input type="text" class="form-control o_input" placeholder="Column title"/>
                     <span class="input-group-append">
                         <button class="btn btn-primary o_kanban_add" type="button">Add</button>
                     </span>