fix(ci): use SimpleCov add_filter and git html2rss pin

Replace invalid skip_filter with add_filter so ruby and openapi CI jobs
load spec_helper; keep html2rss on feat/registry-v1 until gem release.

Author: gildesmarais

Gemfile

@@ -4,8 +4,8 @@ source 'https://rubygems.org'
 
 git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 
+# Until rubygems 0.28.0: git branch; local monorepo: BUNDLE_LOCAL__HTML2RSS=/path/to/html2rss
 gem 'html2rss', github: 'html2rss/html2rss', branch: 'feat/registry-v1'
-# Local monorepo override: BUNDLE_LOCAL__HTML2RSS=/path/to/html2rss
 
 gem 'base64'
 gem 'rack-cache'

spec/spec_helper.rb

@@ -14,8 +14,8 @@
     add_group 'App', 'app'
     add_group 'Config', 'config'
 
-    skip_filter %r{/spec/}
-    skip_filter %r{/config/}
+    add_filter %r{/spec/}
+    add_filter %r{/config/}
 
     minimum_coverage line: 80, branch: 70 unless ENV['OPENAPI']
     maximum_coverage_drop line: 5, branch: 5 unless ENV['OPENAPI']