mastodon api tests: invalidate user cache prior to importing a test reply

This is needed to ensure the user cache does not throw nil when creating the mentions
list.

Signed-off-by: lain <lain@soykaf.club>

test/web/mastodon_api/status_view_test.exs

@@ -60,6 +60,9 @@ test "contains mentions" do
     recipient = "https://pleroma.soykaf.com/users/lain"
     user = User.get_cached_by_ap_id(recipient) || insert(:user, %{ap_id: recipient})
 
+    # invalidate the cache
+    User.invalidate_cache(user)
+
     {:ok, [activity]} = OStatus.handle_incoming(incoming)
 
     status = StatusView.render("status.json", %{activity: activity})