const/vendor: drop version directives from the generated tables and their templates #1884

The owner ruled on #1872 that the vendor templates under pcapkit/vendor/** and the generated pcapkit/const/** files take no versionadded/versionchanged directives, because the scripts regenerate them.

Several templates on main still carry them, each mirrored in its const file:

• ftp/command
• http/method
• ipv6/extension_header
• pcapng/option_type
• pcapng/tls_key_label
• reg/apptype/apptype
• tcp/flags

Find them with git grep -n -E 'version(added|changed|removed)' -- pcapkit/vendor pcapkit/const.

Fix: remove each directive from the template and from the generated file identically, without re-crawling, and update any test that pins the text. Where a directive records a change users need to know about, move the note to the hand-written docs/source/pcapkit/const/*.rst page, as #1872 does. Keep the #: notes on MAX_RETRY and the CI-mode flag in pcapkit/vendor/default.py: they document the crawler framework's own settings, not a template.

Blocked until #1871 merges, because it edits pcapkit/vendor/reg/apptype/apptype.py.