Revert "Bump html-proofer from 3.19.4 to 5.0.0"

Gemfile.lock

@@ -26,13 +26,9 @@ GEM
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
-    addressable (2.8.1)
-      public_suffix (>= 2.0.2, < 6.0)
+    addressable (2.8.0)
+      public_suffix (>= 2.0.2, < 5.0)
     ast (2.4.2)
-    async (2.1.0)
-      console (~> 1.10)
-      io-event (~> 1.0.0)
-      timers (~> 4.1)
     builder (3.2.4)
     coffee-script (2.4.1)
       coffee-script-source
@@ -42,8 +38,6 @@ GEM
     commonmarker (0.17.13)
       ruby-enum (~> 0.5)
     concurrent-ruby (1.1.10)
-    console (1.15.3)
-      fiber-local
     crass (1.0.6)
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
@@ -77,24 +71,22 @@ GEM
     faraday-rack (1.0.0)
     faraday-retry (1.0.3)
     ffi (1.15.5)
-    fiber-local (1.0.0)
     forwardable-extended (2.6.0)
     gemoji (3.0.1)
     html-pipeline (2.14.2)
       activesupport (>= 2)
       nokogiri (>= 1.4)
-    html-proofer (5.0.0)
+    html-proofer (3.19.4)
       addressable (~> 2.3)
-      async (~> 2.1)
+      mercenary (~> 0.3)
       nokogiri (~> 1.13)
+      parallel (~> 1.10)
       rainbow (~> 3.0)
       typhoeus (~> 1.3)
       yell (~> 2.0)
-      zeitwerk (~> 2.5)
     http_parser.rb (0.8.0)
     i18n (1.12.0)
       concurrent-ruby (~> 1.0)
-    io-event (1.0.9)
     jekyll (4.2.2)
       addressable (~> 2.4)
       colorator (~> 1.0)
@@ -198,7 +190,7 @@ GEM
       ast (~> 2.4.1)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (5.0.0)
+    public_suffix (4.0.7)
     racc (1.6.0)
     rack (2.2.4)
     rack-test (2.0.2)
@@ -249,7 +241,6 @@ GEM
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
     thor (1.2.1)
-    timers (4.3.4)
     typhoeus (1.4.0)
       ethon (>= 0.9.0)
     tzinfo (2.0.5)