[FAB-13214] Change link in upgrade doc

Passage should point to release
notes, not the operations
service doc

Change-Id: I4b161ec7e3c98eff481ee4718454882292eaea49
Signed-off-by: joe-alewine <Joe.Alewine@ibm.com>

Author: joe-alewine

docs/source/upgrading_your_network_tutorial.rst

@@ -59,7 +59,8 @@ updated.
 From an operational perspective, it's worth noting that the process for gathering
 logs has changed in v1.4, from ``CORE_LOGGING_LEVEL`` (for the peer) and
 ``ORDERER_GENERAL_LOGLEVEL`` (for the orderer) to ``FABRIC_LOGGING_SPEC`` (the new
-operations service). For more information, check out :doc:`operations_service`.
+operations service). For more information, check out the
+`Fabric release notes <https://github.com/hyperledger/fabric/releases/tag/v1.4.0>`_.
 
 Prerequisites
 ~~~~~~~~~~~~~