Bump html-proofer from 3.15.2 to 3.15.3

Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.15.2 to 3.15.3.
- [Release notes](https://github.com/gjtorikian/html-proofer/releases)
- [Commits](gjtorikian/html-proofer@v3.15.2...v3.15.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

Gemfile.lock

@@ -13,7 +13,7 @@ GEM
     eventmachine (1.2.7)
     ffi (1.12.2)
     forwardable-extended (2.6.0)
-    html-proofer (3.15.2)
+    html-proofer (3.15.3)
       addressable (~> 2.3)
       mercenary (~> 0.3)
       nokogumbo (~> 2.0)
@@ -60,7 +60,7 @@ GEM
     parallel (1.19.1)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.3)
+    public_suffix (4.0.4)
     rainbow (3.0.0)
     rb-fsevent (0.10.3)
     rb-inotify (0.10.0)