Update ordering service docs (#4846)

- Remove references to Kafka.
- Mention CFT and BFT options.

Signed-off-by: David Enyeart <enyeart@us.ibm.com>

docs/source/glossary.rst

@@ -444,9 +444,8 @@ Ordering Service
 Also known as **orderer**. A defined collective of nodes that orders transactions into a block
 and then distributes blocks to connected peers for validation and commit. The ordering service
 exists independent of the peer processes and orders transactions on a first-come-first-serve basis
-for all channels on the network.  It is designed to support pluggable implementations beyond the
-out-of-the-box Kafka and Raft varieties. It is a common binding for the overall network; it
-contains the cryptographic identity material tied to each Member_.
+for all channels on the network. It is designed to support pluggable implementations
+with crash fault tolerant (CFT) and byzantine fault tolerant (BFT) options.
 
 .. _Organization:
 
@@ -575,10 +574,7 @@ New for v1.4.1, Raft is a crash fault tolerant (CFT) ordering service
 implementation based on the `etcd library <https://coreos.com/etcd/>`_
 of the `Raft protocol <https://raft.github.io/raft.pdf>`_. Raft follows a
 "leader and follower" model, where a leader node is elected (per channel) and
-its decisions are replicated by the followers. Raft ordering services should
-be easier to set up and manage than Kafka-based ordering services, and their
-design allows organizations to contribute nodes to a distributed ordering
-service.
+its decisions are replicated by the followers.
 
 .. _SDK:
 

docs/source/ops_guide.rst

@@ -23,5 +23,3 @@ Operations Guides
    enable_tls
    raft_configuration.md
    bft_configuration.md
-   kafka_raft_migration.md
-   kafka

docs/source/orderer/ordering_service.md

@@ -191,9 +191,7 @@ implementation the node will be used in), check out [our documentation on deploy
   based on an implementation of [Raft protocol](https://raft.github.io/raft.pdf)
   in [`etcd`](https://coreos.com/etcd/). Raft follows a "leader and
   follower" model, where a leader node is elected (per channel) and its decisions
-  are replicated by the followers. Raft ordering services should be easier to set
-  up and manage than Kafka-based ordering services, and their design allows
-  different organizations to contribute nodes to a distributed ordering service.
+  are replicated by the followers.
 
 * **BFT** (New as of v3.0)
 

docs/source/whatis.md

@@ -282,8 +282,6 @@ particular deployment or solution. This modular architecture allows the platform
 to rely on well-established toolkits for CFT (crash fault-tolerant) or BFT
 (byzantine fault-tolerant) ordering.
 
-Fabric currently offers a CFT ordering service implementation
-based on the [`etcd` library](https://coreos.com/etcd/) of the [Raft protocol](https://raft.github.io/raft.pdf).
 For information about currently available ordering services, check
 out our [conceptual documentation about ordering](./orderer/ordering_service.html).