[avro] Incorrect version in crate.io landing page

[alamb]

Describe the bug
The readme that appears on https://crates.io/crates/arrow-avro has the wrong version in the usage instructions:

To Reproduce
The page is under the arrow-avro 57 release, but it instructs readers to use the 56 release:

Expected behavior
Should be the correct version

Additional context
cc @jecsand838

[jecsand838]

take

[alamb]

label_issue.py automatically added labels {'arrow'} from #8695

[alamb]

label_issue.py automatically added labels {'arrow-avro'} from #8695