[about:credits] Change the hovering cursor on "show license" from an arrow to a hand.

Bug: 732241
Change-Id: Ie525bd9ca1811581a1d8fbe4a9c02be768032ed9
Reviewed-on: https://chromium-review.googlesource.com/531066Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Commit-Queue: Yipeng Wang <yipengw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478710}

components/about_ui/resources/about_credits.tmpl

@@ -66,12 +66,14 @@ input + label + div {
 }
 input + label::after {
   content: "show license";
+  cursor: pointer;
 }
 input:checked + label + div {
   display: block;
 }
 input:checked + label::after {
   content: "hide license";
+  cursor: pointer;
 }
 </style>
 </head>