ARROW-10285: [Python] Fix usage of deprecated num_children in pyarrow.orc submodule
ARROW-10285: [Python] Fix usage of deprecated num_children in pyarrow.orc submodule

Closes #8441 from jorisvandenbossche/ARROW-10285

Authored-by: Joris Van den Bossche <36c737f86d71d8ee1ddeb1e5c83102ee5de8f97c@gmail.com>
Signed-off-by: Krisztián Szűcs <6bab32dc957a05a87930e779f272342e159326fa@gmail.com>

apache/arrow,laurentgo/arrow,apache/arrow,kou/arrow,cpcloud/arrow,xhochy/arrow,wesm/arrow,icexelloss/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,kou/arrow,wesm/arrow,icexelloss/arrow,icexelloss/arrow,apache/arrow,laurentgo/arrow,xhochy/arrow,laurentgo/arrow,apache/arrow,cpcloud/arrow,kou/arrow,apache/arrow,kou/arrow,cpcloud/arrow,wesm/arrow,laurentgo/arrow,cpcloud/arrow,wesm/arrow,kou/arrow,kou/arrow,xhochy/arrow,xhochy/arrow,kou/arrow,wesm/arrow,cpcloud/arrow,xhochy/arrow,xhochy/arrow,xhochy/arrow,wesm/arrow,icexelloss/arrow,laurentgo/arrow,wesm/arrow,apache/arrow,xhochy/arrow,kou/arrow,xhochy/arrow,cpcloud/arrow,icexelloss/arrow,laurentgo/arrow,xhochy/arrow,cpcloud/arrow,apache/arrow,kou/arrow,cpcloud/arrow,laurentgo/arrow,wesm/arrow,xhochy/arrow,wesm/arrow,laurentgo/arrow,laurentgo/arrow,icexelloss/arrow,laurentgo/arrow,icexelloss/arrow,apache/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow,laurentgo/arrow,laurentgo/arrow,kou/arrow,apache/arrow,icexelloss/arrow,wesm/arrow,cpcloud/arrow,kou/arrow,laurentgo/arrow,kou/arrow,apache/arrow,icexelloss/arrow,icexelloss/arrow,apache/arrow,xhochy/arrow,xhochy/arrow,xhochy/arrow,icexelloss/arrow,cpcloud/arrow,cpcloud/arrow,laurentgo/arrow,laurentgo/arrow,wesm/arrow,wesm/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow,cpcloud/arrow,xhochy/arrow,icexelloss/arrow,apache/arrow