Fix typo in entrypoints-contracts.md

Fixed typo - word should be out:

Original:

follows a first in, first our ordering

Updated:

follows a first in, first out ordering

changelog/1637666096

+author: "@mweichert"
+merge_request: "1298"
+title: "Fix typo in entrypoints-contracts.md"
+type: "added"
\ No newline at end of file