[Format] Clarify allowed values for time types

[asfimport]

See vote and decision on the ML :
https://mail-archives.apache.org/mod_mbox/arrow-dev/202108.mbox/%3C114bcacb-9cb1-55d3-9368-3220c7bec9bc%40python.org%3E

Reporter: Antoine Pitrou / @pitrou
Assignee: Antoine Pitrou / @pitrou

Related issues:

• [Rust] Validate temporal data that has restrictions (relates to)
• [C++] Validate temporal data in ValidateArrayFull (relates to)

PRs and other links:

• GitHub Pull Request #10984

_{Note: This issue was originally created as ARROW-13734. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 10984
#10984