docs: [google-cloud-batch] Rephrase reservation field doc (#13311)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 700712274

Source-Link:
googleapis/googleapis@81e2500

Source-Link:
googleapis/googleapis-gen@ef2cb66
Copy-Tag:
eyJwIjoicGFja2FnZXMvZ29vZ2xlLWNsb3VkLWJhdGNoLy5Pd2xCb3QueWFtbCIsImgiOiJlZjJjYjY2ZmViOTliZWQ2NTk5NDhmNDRjNWIwYWMxM2ZiM2RmNTkxIn0=

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

packages/google-cloud-batch/google/cloud/batch_v1alpha/types/job.py

@@ -871,10 +871,10 @@ class InstancePolicy(proto.Message):
                 file system or a raw storage drive that is not
                 ready for data storage and accessing.
             reservation (str):
-                Optional. If specified, VMs will consume only the specified
-                reservation. If not specified (default), VMs will consume
-                any applicable reservation. Additionally, VMs will not
-                consume any reservation if "NO_RESERVATION" is specified.
+                Optional. If not specified (default), VMs will consume any
+                applicable reservation. If "NO_RESERVATION" is specified,
+                VMs will not consume any reservation. Otherwise, if
+                specified, VMs will consume only the specified reservation.
         """
 
         allowed_machine_types: MutableSequence[str] = proto.RepeatedField(