autopkgtest: Remove all-proposed for noble

We have migrated most, so let's stop doing this.

britney2/policies/autopkgtest.py

@@ -1130,11 +1130,6 @@ class AutopkgtestPolicy(BasePolicy):
             qname = 'debci-huge-%s-%s' % (self.options.series, arch)
         else:
             qname = 'debci-%s-%s' % (self.options.series, arch)
-        # FIXME: Remove after the time_t transition
-        if (self.options.series == "noble" and
-                "migration-reference/0" not in triggers and
-                datetime.utcnow().date() < date(2024, 4, 4)):
-            params["all-proposed"] = "1"
         params['submit-time'] = datetime.strftime(datetime.utcnow(), '%Y-%m-%d %H:%M:%S%z')
 
         if self.amqp_channel: