Do not apply skip-unless-changed for cron triggers.

src/taskgraph/optimize/strategies.py

@@ -80,8 +80,8 @@ def check(self, files_changed, patterns):
         return False
 
     def should_remove_task(self, task, params, file_patterns):
-        # pushlog_id == -1 - this is the case when run from a cron.yml job or on a git repository
-        if params.get("repository_type") == "hg" and params.get("pushlog_id") == -1:
+        # skip-unless-changed should not apply to cron tasks (there will never be file changes)
+        if params.get("tasks_for") == "cron":
             return False
 
         changed = self.check(params["files_changed"], file_patterns)