Bump utils to 51.2.1

This brings a few performance improvements for RecipientCSV, which
we use to preview and process CSVs. One change also renames one of
the attributes for the class to "guestlist".

app/main/views/send.py

@@ -652,7 +652,7 @@ def _check_messages(service_id, template_id, upload_id, preview_row, letters_as_
         template=template,
         max_initial_rows_shown=50,
         max_errors_shown=50,
-        whitelist=itertools.chain.from_iterable(
+        guestlist=itertools.chain.from_iterable(
             [user.name, user.mobile_number, user.email_address] for user in Users(service_id)
         ) if current_service.trial_mode else None,
         remaining_messages=remaining_messages,

app/main/views/uploads.py

@@ -451,7 +451,7 @@ def check_contact_list(service_id, upload_id):
     recipients = RecipientCSV(
         contents,
         template=get_sample_template(template_type or 'sms'),
-        whitelist=itertools.chain.from_iterable(
+        guestlist=itertools.chain.from_iterable(
             [user.name, user.mobile_number, user.email_address]
             for user in current_service.active_users
         ) if current_service.trial_mode else None,

requirements.in

@@ -30,7 +30,7 @@ pyproj==3.2.1
 # PaaS
 awscli-cwlogs>=1.4,<1.5
 itsdangerous==1.1.0  # pyup: <2
-notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@50.0.0
+notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@51.2.1
 govuk-frontend-jinja @ git+https://github.com/alphagov/govuk-frontend-jinja.git@v0.5.8-alpha
 
 # cryptography 3.4+ incorporates Rust code, which isn't supported on PaaS

requirements.txt

@@ -123,7 +123,7 @@ mistune==0.8.4
     # via notifications-utils
 notifications-python-client==6.3.0
     # via -r requirements.in
-notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@50.0.0
+notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@51.2.1
     # via -r requirements.in
 openpyxl==3.0.7
     # via pyexcel-xlsx