Merge branch 'ks/ref-filter-sort-numerically' into maint-2.42

"git for-each-ref --sort='contents:size'" sorts the refs according
to size numerically, giving a ref that points at a blob twelve-byte
(12) long before showing a blob hundred-byte (100) long.

* ks/ref-filter-sort-numerically:
  ref-filter: sort numerically when ":size" is used