textproc/ripgrep: Fix build with rust 1.71.0

Summary:
Do not abort if documentation is missing.

error: missing documentation for an extern crate

--> crates/grep/src/lib.rs:17:1
 |

17 | pub extern crate grep_cli as cli;

| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|

PR: 272602
Reviewed by: mikael
Approved by: portmgr (build fix blanket)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D41095