[FAB-13357] Fixed error in fabric gossip documentation

In fabric's Gossip data dissemination protocol documentation,
under "Static leader election", point #2 had wrong variables,
both being CORE_PEER_GOSSIP_USELEADERELECTION. The second variable
has been updated to CORE_PEER_GOSSIP_ORGLEADER

Change-Id: I1be381ed3da1face2b1fc2210a5d783c7693e8f5
Signed-off-by: Amol Pednekar <amol_pednekar@persistent.com>

docs/source/gossip.rst

@@ -90,7 +90,7 @@ Alternatively these parameters could be configured and overridden with environme
     export CORE_PEER_GOSSIP_USELEADERELECTION=false
     export CORE_PEER_GOSSIP_ORGLEADER=false
 
-2. Setting ``CORE_PEER_GOSSIP_USELEADERELECTION`` and ``CORE_PEER_GOSSIP_USELEADERELECTION``
+2. Setting ``CORE_PEER_GOSSIP_USELEADERELECTION`` and ``CORE_PEER_GOSSIP_ORGLEADER``
    with ``true`` value is ambiguous and will lead to an error.
 3. In static configuration organization admin is responsible to provide high availability
    of the leader node in case for failure or crashes.