Chrome Desktop UI: fix button margin on chrome://interventions-internals/ page

Bug: 1049960
Change-Id: I326731a647f8d048b902f1448f6da944946d1207
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145159Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Yuheng Huang <yuhengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814208}

chrome/browser/resources/interventions_internals/index.css

@@ -35,7 +35,7 @@ button {
   color: white;
   font-size: 65%;
   font-weight: bold;
-  margin: 5px 0;
+  margin: 5px 2px;
   padding: 5px;
   text-align: center;
   text-decoration: none;