Replace <code> with {@code} in javadoc

{@code foo} is shorter and easier to read and write than
<code>foo</code>, which is why it was introduced years ago in the
javadoc processor.  Make consistent use of it throughout the
documentation comments.

Change-Id: I59d428cb6c5015453629398b0697891b83c8e91d

gerrit-openid/src/main/java/com/google/gerrit/httpd/auth/openid/OpenIdLoginServlet.java

@@ -24,7 +24,7 @@ import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-/** Handles the <code>/OpenID</code> URL for web based single-sign-on. */
+/** Handles the {@code /OpenID} URL for web based single-sign-on. */
 @SuppressWarnings("serial")
 @Singleton
 class OpenIdLoginServlet extends HttpServlet {