Retitle choose sender page as first page in flow

We have a sort of principle that when clicking a link, the page you land
on should be titled the same as the link you clicked.

This also reduces unnecessary repetition between the page title and the
form label.

app/main/views/send.py

@@ -217,17 +217,17 @@ def set_sender(service_id, template_id):
 def get_sender_context(sender_details, template_type):
     context = {
         'email': {
-            'title': "Choose where to send replies",
+            'title': 'Send to one recipient',
             'description': 'Where should replies go?',
             'field_name': 'email_address'
         },
         'letter': {
-            'title': 'Choose sender address',
+            'title': 'Send to one recipient',
             'description': 'What should appear in the top right of the letter?',
             'field_name': 'contact_block'
         },
         'sms': {
-            'title': 'Chose text message sender',
+            'title': 'Send to one recipient',
             'description': 'Who should the message come from?',
             'field_name': 'sms_sender'
         }

tests/app/main/views/test_send.py

@@ -44,13 +44,13 @@ test_non_spreadsheet_files = glob(path.join('tests', 'non_spreadsheet_files', '*
     (
         mock_get_service_email_template,
         multiple_reply_to_email_addresses,
-        'Choose where to send replies',
+        'Send to one recipient',
         'Where should replies go?',
     ),
     (
         mock_get_service_template,
         multiple_sms_senders,
-        'Chose text message sender',
+        'Send to one recipient',
         'Who should the message come from?'
     )
 ])