[ruby/irb] Remove encoding_aliases.rb

(https://github.com/ruby/irb/pull/569)

We don't have to load another file to define the legacy encoding aliases
map because there's only one definition of it. We can define it in
locale.rb directly.

lib/irb/lc/ja/encoding_aliases.rb

@@ -1,13 +0,0 @@
-# frozen_string_literal: false
-module IRB
-  # :stopdoc:
-
-  class Locale
-    @@legacy_encoding_alias_map = {
-      'ujis' => Encoding::EUC_JP,
-      'euc' => Encoding::EUC_JP
-    }.freeze
-  end
-
-  # :startdoc:
-end

lib/irb/locale.rb

@@ -15,7 +15,11 @@ module IRB # :nodoc:
     ]x
     LOCALE_DIR = "/lc/"
 
-    @@legacy_encoding_alias_map = {}.freeze
+    LEGACY_ENCODING_ALIAS_MAP = {
+      'ujis' => Encoding::EUC_JP,
+      'euc' => Encoding::EUC_JP
+    }
+
     @@loaded = []
 
     def initialize(locale = nil)
@@ -26,8 +30,7 @@ module IRB # :nodoc:
         @lang, @territory, @encoding_name, @modifier = m[:language], m[:territory], m[:codeset], m[:modifier]
 
         if @encoding_name
-          begin load 'irb/encoding_aliases.rb'; rescue LoadError; end
-          if @encoding = @@legacy_encoding_alias_map[@encoding_name]
+          if @encoding = LEGACY_ENCODING_ALIAS_MAP[@encoding_name]
             warn(("%s is obsolete. use %s" % ["#{@lang}_#{@territory}.#{@encoding_name}", "#{@lang}_#{@territory}.#{@encoding.name}"]), uplevel: 1)
           else
             @encoding = Encoding.find(@encoding_name) rescue nil