capes/overlays/relay: fix headers

boards/capes/overlays/relay.rst

 .. _bone-cape-relay:
 
 BeagleBoard.org BeagleBone Relay Cape
-#########
+#####################################
 
 Relay Cape, as the name suggests, is a simple Cape with a relay on it.
 It contains four relays, each of which can be operated independently from the BeagleBone.
@@ -16,7 +16,7 @@ How to Use
 ---------------
 
 Installation
-******
+************
 
 No special configuration is required. When you plug Cape into your BeagleBoard, 
 it is automatically recognized by the Cape Universal function.
@@ -57,4 +57,4 @@ This allows you to adjust the brightness;
 entering 1 for brightness turns it ON, and entering 0 for OFF.
 
 The four relays can be changed individually 
-by changing the number after "relay.
+by changing the number after "relay.
\ No newline at end of file