fix(a11y.color): corrige le manque de contraste sur les libelles des liens dans les menu action

app/assets/stylesheets/buttons.scss

@@ -259,11 +259,6 @@
       border-bottom: none;
     }
 
-    a {
-      color: $dark-grey;
-      background-image: none; // remove DSFR underline
-    }
-
     // Make child links fill the whole clickable area
     > a {
       display: flex;

app/assets/stylesheets/dossiers_table.scss

@@ -13,10 +13,6 @@
     padding: 0;
   }
 
-  thead a {
-    color: #000000;
-  }
-
   a {
     background-image: none; // remove DSFR underline
   }
@@ -28,7 +24,6 @@
   }
 
   .cell-link {
-    color: $black;
     // In order to have identical height in the table header and the table rows,
     // we compensate for the height difference between the biggest element of the header
     // (the Personnaliser button, 38px) and the biggest cell-link element of the rows (the label, 28px)