api-ref: Fix namespace parameter for backend capabilities

This patch set corrects the namespace parameter for capabilities
api-ref from namespace [0] to namespace_1 which is the correct
one as it is both required and matches the following format
in the view code [2]:

    The storage namespace, such as
    ``OS::Storage::Capabilities::foo``.

[0] https://github.com/openstack/cinder/blob/7f7716d584cd955162cab988c49c6fa3ac08f2e0/api-ref/source/v3/parameters.yaml#L1945
[1] https://github.com/openstack/cinder/blob/7f7716d584cd955162cab988c49c6fa3ac08f2e0/api-ref/source/v3/parameters.yaml#L1951
[2] https://github.com/openstack/cinder/blob/af41c04d0ff0b5a4b2077eedb605314937912a35/cinder/api/views/capabilities.py#L31

Change-Id: I0557b32e7e3752e8fcde5dadd621c82fded1e755

api-ref/source/v2/capabilities-v2.inc

@@ -37,7 +37,7 @@ Response Parameters
    - pool_name: pool_name
    - description: description
    - volume_backend_name: volume_backend_name
-   - namespace: namespace
+   - namespace: namespace_1
    - visibility: visibility
    - driver_version: driver_version
    - vendor_name: vendor_name

api-ref/source/v3/capabilities-v3.inc

@@ -37,7 +37,7 @@ Response Parameters
    - pool_name: pool_name
    - description: description_10
    - volume_backend_name: volume_backend_name
-   - namespace: namespace
+   - namespace: namespace_1
    - visibility: visibility
    - driver_version: driver_version
    - vendor_name: vendor_name