net/ruby-recog: update to 2.3.21

2.3.21 (2021-08-02)

Highlights:

* BUG: Fix a very unlikely DoS condition, general regex performance tuning
  (#368)
* Regex cross-language compatibility (#367)
* Field migration: host.id -> hw.serial_number (#366)
* Fingerprints: Misc improvements (Thanks @jpincombe-r7) (#363 #365)
* CPE: Updates using the current NIST database.

(taca)