Allow acq-* to relate physio data to MRI data in anat/ as describ…

…ed in #2164

The deno based validator did not accept files like `sub-01_acq-T1w_physio.tsv.gz` located in `anat/` and related to the T1w anatomy. This was, because a task was required, which was inherited from `rules.files.raw.task.timeseries.entities`. The key task is now overridden to optional. Please also see issue #2164 for more information and related patches.

src/schema/rules/files/raw/task.yaml

@@ -112,6 +112,7 @@ timeseries__anat:
     echo: optional
     part: optional
     chunk: optional
+    task: optional
 
 timeseries__func:
   $ref: rules.files.raw.task.timeseries