Update RuboCop 0.52.1 -> 0.54.0 for CI

Author: sds

.rubocop.yml

@@ -142,5 +142,8 @@ Style/SymbolArray:
 Style/TrailingCommaInArguments:
   Enabled: false
 
-Style/TrailingCommaInLiteral:
+Style/TrailingCommaInArrayLiteral:
+  Enabled: false
+
+Style/TrailingCommaInHashLiteral:
   Enabled: false

Gemfile

@@ -10,4 +10,4 @@ gem 'rspec', '~> 3.0'
 gem 'coveralls', '~> 0.8'
 
 # Pin RuboCop for Travis builds.
-gem 'rubocop', '0.52.1'
+gem 'rubocop', '0.54.0'

lib/overcommit/configuration_loader.rb

@@ -12,7 +12,7 @@ class << self
       #
       # @return [Overcommit::Configuration]
       def default_configuration
-        @default_config ||= load_from_file(DEFAULT_CONFIG_PATH, default: true, verify: false)
+        @default_configuration ||= load_from_file(DEFAULT_CONFIG_PATH, default: true, verify: false)
       end
 
       # Loads configuration from file.

lib/overcommit/hook/pre_commit/license_header.rb

@@ -37,7 +37,7 @@ def license_file
     end
 
     def license_lines
-      @license_regex ||= begin
+      @license_lines ||= begin
         file_root = Overcommit::Utils.convert_glob_to_absolute(license_file)
         File.read(file_root).split("\n")
       end

lib/overcommit/os.rb

@@ -27,7 +27,7 @@ def linux?
       private
 
       def host_os
-        @os ||= ::RbConfig::CONFIG['host_os'].freeze
+        @host_os ||= ::RbConfig::CONFIG['host_os'].freeze
       end
     end