WIP: Fix some Mocha deprecation warnings

This fixes some of the warnings related to strict keyword argument
matching, like this one:

    Mocha deprecation warning at app/services/asset_manager/attachment_updater/update.rb:15:in `call':
    Expectation defined at test/unit/services/asset_manager/attachment_updater/draft_status_updates_test.rb:28:
    in `block (3 levels) in <class:DraftStatusUpdatesTest>'
    expected keyword arguments ("draft" => true),
    but received positional hash ({"draft" => true}).
    These will stop matching when strict keyword argument matching is enabled.
    See the documentation for Mocha::Configuration#strict_keyword_argument_matching=.

In order to fix the warnings, I've changed the signature of
AssetManager::AssetUpdater#call so that new_attributes parameter must be supplied
as keyword arguments rather than a positional Hash. This had the
advantage that I only needed to change
AssetManager::AttachmentUpdater::Update#call to convert the
deep_stringify_keys into keyword arguments using a double-splat; I
didn't need to change all the places where
AssetManager::AssetUpdater#call is stubbed.

An alternative would be to leave the signature of
AssetManager::AssetUpdater#call unchanged and change the calls to
Expectation#with for all the relevant stubs to pass a positional Hash,
i.e. wrapped in braces.

This article [1] is a very useful reference.

[1]: https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/

app/services/asset_manager/asset_updater.rb

@@ -13,11 +13,11 @@ def initialize(attachment_data_id, legacy_url_path)
     end
   end
 
-  def self.call(*args)
-    new.call(*args)
+  def self.call(...)
+    new.call(...)
   end
 
-  def call(asset_data, legacy_url_path, new_attributes = {})
+  def call(asset_data, legacy_url_path, **new_attributes)
     attributes = find_asset_by(legacy_url_path)
     asset_deleted = attributes["deleted"]
 

app/services/asset_manager/attachment_updater/update.rb

@@ -15,7 +15,7 @@ def call
     AssetManager::AssetUpdater.call(
       attachment_data,
       legacy_url_path,
-      new_attributes.deep_stringify_keys,
+      **new_attributes.deep_stringify_keys,
     )
   end