chore: remove legacy REST API version shim for servers pre-2.4

[jacalata]

Summary

Remove the compatibility shim that supports connecting to Tableau Server versions that predate REST API 2.4 (i.e., Tableau Server 10.0 and earlier, released before 2017).

Background

server.py currently has:

_PRODUCT_TO_REST_VERSION = {
    "10.0": "2.3",
    "9.3": "2.2",
    ...
}
minimum_supported_server_version = "2.3"
default_server_version = "2.4"  # first version that dropped the legacy auth endpoint

The _get_legacy_version() method hits /auth?format=xml — a pre-2.4 endpoint — because servers that old don't support the standard /serverinfo REST API endpoint. _determine_highest_version() falls back to this when serverInfo returns a 404.

What to remove

• _PRODUCT_TO_REST_VERSION dict
• _get_legacy_version() method
• The two except branches in _determine_highest_version() that call _get_legacy_version()
• Raise minimum_supported_server_version to "2.4" (or "3.0" — see below)
• Update default_server_version to match

Impact on users

None, unless they are connecting to Tableau Server 10.0 (released 2016) or earlier. Tableau Server 10.x reached end of life in 2019. All currently-supported Tableau Server versions use REST API 3.x.

Note: the @api(version="2.x") decorators on endpoint methods are minimum version requirements, not upper bounds — they are unaffected by this change and no endpoint methods are removed.

Decision needed

Should minimum_supported_server_version be raised to "2.4" (first version with /serverinfo) or "3.0" (Tableau Server 2018.1, 6+ years old)? The code change is identical either way; the difference is only the documented policy.