Bump nokogiri from 1.8.5 to 1.9.1 (#9557)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.8.5 to 1.9.1.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.8.5...v1.9.1)

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

Gemfile

@@ -57,7 +57,7 @@ gem 'idn-ruby', require: 'idn'
 gem 'kaminari', '~> 1.1'
 gem 'link_header', '~> 0.0'
 gem 'mime-types', '~> 3.2', require: 'mime/types/columnar'
-gem 'nokogiri', '~> 1.8'
+gem 'nokogiri', '~> 1.9'
 gem 'nsa', '~> 0.2'
 gem 'oj', '~> 3.7'
 gem 'ostatus2', '~> 2.0'

Gemfile.lock

@@ -343,7 +343,7 @@ GEM
     mime-types-data (3.2018.0812)
     mimemagic (0.3.2)
     mini_mime (1.0.1)
-    mini_portile2 (2.3.0)
+    mini_portile2 (2.4.0)
     minitest (5.11.3)
     msgpack (1.2.4)
     multi_json (1.13.1)
@@ -354,8 +354,8 @@ GEM
       net-ssh (>= 2.6.5)
     net-ssh (5.0.2)
     nio4r (2.3.1)
-    nokogiri (1.8.5)
+    nokogiri (1.9.1)
-      mini_portile2 (~> 2.3.0)
+      mini_portile2 (~> 2.4.0)
     nokogumbo (2.0.0)
       nokogiri (~> 1.8, >= 1.8.4)
     nsa (0.2.4)
@@ -709,7 +709,7 @@ DEPENDENCIES
   microformats (~> 4.0)
   mime-types (~> 3.2)
   net-ldap (~> 0.10)
-  nokogiri (~> 1.8)
+  nokogiri (~> 1.9)
   nsa (~> 0.2)
   oj (~> 3.7)
   omniauth (~> 1.9)