Merge `-xfails.txt` in this repository and array-api-tests

[ev-br]

We have two sets of skip files for array-api-tests:

$ ll ../array-api-tests/array-api-strict-skips.txt 
-rw-rw-r-- 1 br br 4796 янв 30 18:28 ../array-api-tests/array-api-strict-skips.txt
$ ll *-xfails.txt
-rw-rw-r-- 1 br br 4597 янв 30 20:34 array-api-tests-xfails.txt

Should merge them, really.

[ev-br]

fixed by data-apis/array-api-tests#421