ci(doc-linter): delete lint_AS placeholder

`lint_AS()` and its `NUMBER` regex were a placeholder for a
future AS-number documentation-range check (RFC 5398).
`lint_AS()` was never called from anywhere — it'd merely
`pass` on `re.search` hit. Pure dead code that made it look
like AS-number linting existed when it didn't.

Delete:
- the `NUMBER` regex constant
- the `lint_AS()` function

If/when AS-number linting is actually desired, implement it
properly: hook into the lint loop in `handle_file_action()`,
return the standard `(message, line, severity)` tuple on
violations, and define the allowed AS ranges from
`/^AGENTS.md/` (currently 64496–64511 and 65536–65551).

Tracked as item 8 of the rolling-side cleanup backlog from
PR #2014 / #2019 / #2020 reviews.

🤖 Generated by [robots](https://vyos.io)

(cherry picked from commit 61ecb4e103c6a6225b3d71586f7f65e41c3e3510)

1 files changed, 0 insertions, 8 deletions

diff --git a/scripts/doc-linter.py b/scripts/doc-linter.py
index 790409de..2214a851 100644
--- a/scripts/doc-linter.py
+++ b/scripts/doc-linter.py
@@ -117,14 +117,6 @@ def lint_ipv6(cnt, line):
         return (f"Use IPv6 reserved for Documentation (RFC 3849) or private Space: {ip}", cnt, 'error')
 
 
-def lint_AS(cnt, line):
-    """Placeholder for future AS-number documentation-range checks (RFC 5398)."""
-    number = re.search(NUMBER, line, re.I)
-    if number:
-        pass
-        # find a way to detect AS numbers
-
-
 def lint_linelen(cnt, line):
     """Warn when a line exceeds the 80-character docs convention."""
     line = line.rstrip()