[deps]: Update nkf to v0.3.0 (#7475)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Gemfile

@@ -15,7 +15,7 @@ gem 'mutex_m', '0.3.0'
 gem 'csv', '3.3.6'
 
 # Since ruby 3.4.1 these are not included in the standard library
-gem 'nkf', '0.2.0'
+gem 'nkf', '0.3.0'
 
 # Starting with Ruby 3.5.0, these are not included in the standard library
 gem 'ostruct', '0.6.3'

Gemfile.lock

@@ -192,7 +192,7 @@ GEM
     mutex_m (0.3.0)
     nanaimo (0.4.0)
     naturally (2.3.0)
-    nkf (0.2.0)
+    nkf (0.3.0)
     optparse (0.8.1)
     os (1.1.4)
     ostruct (0.6.3)
@@ -269,7 +269,7 @@ DEPENDENCIES
   fastlane-plugin-firebase_app_distribution
   logger (= 1.7.0)
   mutex_m (= 0.3.0)
-  nkf (= 0.2.0)
+  nkf (= 0.3.0)
   ostruct (= 0.6.3)
   time (= 0.4.2)