SideBySide2: Fix max width of comment widget groups

The group should have a max-width of 650px. This allows the group
to show the right side drop shadow on a normally sized window,
making the comment appear to float a bit on the page.

The max width was incorrectly applied to the header line of the
comment, andwas not being used by the browser to size the group.

Change-Id: I564c7fd9b154d64cdf1b20836351f40954a4900d
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CommentBoxUi.css b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CommentBoxUi.css
index 8efc9f7..67b86ed 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CommentBoxUi.css
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CommentBoxUi.css
@@ -14,6 +14,8 @@
  */
 
 .commentWidgets {
+  max-width: 650px;
+
   font-family: sans-serif;
   background-color: #fcfa96;
   border: 1px solid black;
@@ -38,7 +40,6 @@
 }
 
 .header {
-  max-width: 650px;
   cursor: pointer;
 }