Update WEBrick to v1.6.1

Ruby ships with WEBrick v1.6.0, but v1.6.1 contains a fix for a CVE:
https://bugs.ruby-lang.org/issues/17201

We only use WEBrick for Sidekiq exporter to serve internal metrics, so
this CVE shouldn't be a user-facing issue.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/296224

Gemfile

@@ -331,6 +331,7 @@ gem 'snowplow-tracker', '~> 0.6.1'
 # Metrics
 group :metrics do
   gem 'method_source', '~> 1.0', require: false
+  gem 'webrick', '~> 1.6.1', require: false
 
   # Prometheus
   gem 'prometheus-client-mmap', '~> 0.12.0'

Gemfile.lock

@@ -1248,6 +1248,7 @@ GEM
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
+    webrick (1.6.1)
     websocket-driver (0.7.3)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
@@ -1531,6 +1532,7 @@ DEPENDENCIES
   vmstat (~> 2.3.0)
   webauthn (~> 2.3)
   webmock (~> 3.9.1)
+  webrick (~> 1.6.1)
   wikicloth (= 0.8.1)
   yajl-ruby (~> 1.4.1)
 

changelogs/unreleased/sh-upgrade-webrick-1-6-1.yml

+---
+title: Update WEBrick to v1.6.1
+merge_request: 50720
+author:
+type: security