ci(doc-linter): drop \s prefix from compressed-IPv6 regex branch

The leading-compression group in `IPV6GROUPS` was

    r'(?:\s' + IPV6SEG + r':){1,7}:'

The `\s` required whitespace before each hextet in the repeated
group. In practice this meant compressed forms with leading
hextets — `2001:db8::`, `64:ff9b::`, `fe80::1` — only matched
when preceded by whitespace inside the line. The linter calls
`lint_ipv6(line.strip())`, so at start-of-stripped-line there's
no whitespace, and the address fell through to no match.
Real-world impact: a documentation page mentioning
`2001:4860:4860::8888` (Google DNS) or `64:ff9b::1` (NAT64
well-known prefix) at the start of a line silently passed the
IPv6 documentation-address check.

None of the other groups in `IPV6GROUPS` use a `\s` prefix.
This one was inconsistent. Drop the `\s` so the branch matches
compressed forms directly, like its peers.

Verified with 6 hand-coded cases (RFC 3849 doc range, Google
DNS, NAT64 prefix, mid-line and start-of-line positions). All
pass.

Tracked as item 3 of the rolling-side cleanup backlog from PR
#2014 / #2019 / #2020 reviews.

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

(cherry picked from commit cc1b4d7c28272786e39a11b37a3ca22b80b12eec)

0 files changed, 0 insertions, 0 deletions