Update the glossary

doc/python/sphinx/glossary.rst

@@ -29,15 +29,13 @@ Glossary
     and the client-side.
 
   wait_for_ready
-    If an RPC is issued but the channel is in TRANSIENT_FAILURE or SHUTDOWN
-    states, the RPC is unable to be transmitted promptly. By default, gRPC
-    implementations SHOULD fail such RPCs immediately. This is known as "fail
-    fast," but the usage of the term is historical. RPCs SHOULD NOT fail as a
-    result of the channel being in other states (CONNECTING, READY, or IDLE).
+    If an RPC is issued but the channel is in the TRANSIENT_FAILURE or SHUTDOWN
+    states, the library cannot transmit the RPC at the moment. By default, the
+    gRPC library will fail such RPCs immediately. This is known as "fail fast."
+    RPCs will not fail as a result of the channel being in other states
+    (CONNECTING, READY, or IDLE).
 
-    gRPC implementations MAY provide a per-RPC option to not fail RPCs as a
-    result of the channel being in TRANSIENT_FAILURE state. Instead, the
-    implementation queues the RPCs until the channel is READY. This is known as
-    "wait for ready." The RPCs SHOULD still fail before READY if there are
-    unrelated reasons, such as the channel is SHUTDOWN or the RPC's deadline is
-    reached.
+    When the wait_for_ready option is specified, the library will queue RPCs
+    until the channel is READY. Any submitted RPCs may still fail before the
+    READY state is reached for other reasons, e.g., the client channel has been
+    shut down or the RPC's deadline has been reached.