Rename ‘Send a message’ to ‘Templates’ in basic view

From Karl:

> Templates – this should be consistent with Admin view. Users may
> switch from Basic to Admin view (or vice versa), they will also
> interact with users who have a different view or permissions to them.
> Neither should have to learn new interfaces and language if possible.

> ‘Send a message’ was a nice, active label – but Notify options aren’t
> usually actions. If we’re going to change this we should be consistent
> across both Admin and Basic views.

> For the same reason, I have rejected ‘see’, ‘search’ and ‘view sent
> messages’. It will be interesting to see in user testing whether users
> read ‘sent messages’ as ‘send messages’.

tests/app/test_navigation.py

@@ -159,5 +159,5 @@ def test_caseworkers_get_caseworking_navigation(
     )
     page = client_request.get('main.choose_template', service_id=SERVICE_ONE_ID)
     assert normalize_spaces(page.select_one('#content nav').text) == (
-        'Send a message Sent messages'
+        'Templates Sent messages'
     )