chore(deps): upgrade nokogiri

Gemfile.lock

@@ -132,7 +132,7 @@ GEM
     marcel (1.0.1)
     method_source (1.0.0)
     mini_mime (1.1.0)
-    mini_portile2 (2.5.3)
+    mini_portile2 (2.6.1)
     minitest (5.14.4)
     mongo (2.6.2)
       bson (>= 4.3.0, < 5.0.0)
@@ -147,12 +147,12 @@ GEM
       activerecord (>= 3.0.0)
       activesupport (>= 3.0.0)
     nio4r (2.5.8)
-    nokogiri (1.11.7)
+    nokogiri (1.12.5)
-      mini_portile2 (~> 2.5.0)
+      mini_portile2 (~> 2.6.1)
       racc (~> 1.4)
     puma (4.3.10)
       nio4r (~> 2.0)
-    racc (1.5.2)
+    racc (1.6.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)