feedback: Remove unnecessary extra padding.

See screenshot in bug.

TEST=deploy on chromebook, open feedback window.

Fixed: chromium:1138774
Change-Id: I91249d08dbb2bde7ba65b15adf5fed5c43cc1855
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2476565Reviewed-by: Ian Barkley-Yeung <iby@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Miriam Zimmerman <mutexlox@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817621}

chrome/browser/resources/feedback/css/feedback.css

@@ -49,6 +49,10 @@ body {
   margin: 20px;
 }
 
+.content #free-form-text {
+  margin-top: 0;  /* the content frame already gives enough margin. */
+}
+
 .content #description-text {
   border-color: #c8c8c8;
   box-sizing: border-box;