[9.18] fix: nil: Disable clang-format for Local IPv6 Unicast Addresses strings

The LSP server (using clangd) was always complaining about:

    Suspicious string literal, probably missing a comma

for the two Local IPv6 Unicast Addresses strings that spanned
across multiple lines.  Disable clang-format for these two lines.

Backport of MR !10764

Merge branch 'backport-ondrej/fix-suspicious-string-literal-probably-missing-comma-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!10766