upgrade #callout-navbar-overflow from info to warning

docs/components.html

@@ -1254,7 +1254,7 @@ lead: "Over a dozen reusable components built to provide iconography, dropdowns,
   <h2 id="navbar-default">Default navbar</h2>
   <p>Navbars are responsive meta components that serve as navigation headers for your application or site. They begin collapsed (and are toggleable) in mobile views and become horizontal as the available viewport width increases.</p>
 
-  <div class="bs-callout bs-callout-info" id="callout-navbar-overflow">
+  <div class="bs-callout bs-callout-warning" id="callout-navbar-overflow">
     <h4>Overflowing content</h4>
     <p>Since Bootstrap doesn't know how much space the content in your navbar needs, you might run into issues with content wrapping into a second row. To resolve this, you can:</p>
     <ol type="a">