Bump nokogiri from 1.15.4 to 1.15.6 (#346)

Author: dependabot[bot]

Gemfile.lock

@@ -42,15 +42,15 @@ GEM
     loofah (2.21.3)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mini_portile2 (2.8.4)
+    mini_portile2 (2.8.5)
     minitest (5.19.0)
-    nokogiri (1.15.4)
+    nokogiri (1.15.6)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
     parallel (1.22.1)
     parser (3.1.2.1)
       ast (~> 2.4.1)
-    racc (1.7.1)
+    racc (1.7.3)
     rails-dom-testing (2.2.0)
       activesupport (>= 5.0.0)
       minitest