replace border by box-shadox in flex-bloc and flex-table

We use box-shadow instead of border
to avoid to manage border double-width
when blocs are resized for small screen !

Then we can simulate border-collapse: collapse (table)

src/Bundle/ChillPersonBundle/Resources/public/vuejs/AccompanyingCourse/components/Requestor.vue

@@ -144,7 +144,6 @@ div.flex-table {
    }
    div.item-bloc {
       background-color: white !important;
-      border: 1px solid #000;
       padding: 1em;
       margin-top: 1em;
       .content-bloc {