Fix formatting of example blocks

With the new stylesheet example blocks (delimited with ====) are
rendered as rather intrusive boxes with large padding in yellow
and grey.

This patch replaces the example blocks with simple code blocks
(delimited with ----) that better match the overall style of the
documentation.

Change-Id: Id95387cdb153332c2066e2d5e378697647dbca52
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>

Documentation/cmd-plugin-enable.txt

diff --git a/Documentation/cmd-plugin-enable.txt b/Documentation/cmd-plugin-enable.txt
index 508f972..9b52736 100644
--- a/Documentation/cmd-plugin-enable.txt
+++ b/Documentation/cmd-plugin-enable.txt
@@ -31,9 +31,9 @@
 == EXAMPLES
 Enable a plugin:
 
-====
+----
 	ssh -p 29418 localhost gerrit plugin enable my-plugin
-====
+----
 
 GERRIT
 ------