css: Let actions popover icon take maximum possible width & height.

We need to fill width of `actions_hover` with padding of
`zulip-icon`, so that hovering over `.actions_hover` shows you
tooltip and clicking on it shows popover.

static/styles/zulip.css

@@ -1068,6 +1068,15 @@ td.pointer {
         }
     }
 
+    .actions_hover {
+        line-height: 1;
+
+        .zulip-icon-ellipsis-v-solid {
+            padding: 2px 5.33px;
+            outline: none;
+        }
+    }
+
     /* Tooltips should not follow the width restrictions of their parent element. */
     [data-tippy-root] {
         width: max-content;