Adjust hover styles in table actions

The underline text decoration looked a bit strange with the icon on top
of it, and we had an inconsistency since links had a text decoration but
buttons didn't. I think we can remove it since both the color of the
icon and the cursor change on hover and that's enough feedback.

And we were accidentally overwriting the color of the investments link
on hover and focus.

app/assets/stylesheets/admin/table_actions.scss

@@ -19,6 +19,7 @@
     &:hover,
     &:focus {
       color: $link-hover;
+      text-decoration: none;
     }
 
     &::before {
@@ -77,7 +78,7 @@
   .investments-link {
     color: darken($warning-color, 20%);
 
-    &::before {
+    &:not(:hover, :focus)::before {
       color: $warning-color;
     }
   }