Fix remaining RuboCop issues

bundler/lib/bundler/templates/newgem/Gemfile.tt

@@ -9,9 +9,11 @@ gem "rake", "~> 13.0"
 <%- if config[:ext] -%>
 gem "rake-compiler"
 <%- end -%>
+
 <%- if config[:test] -%>
 gem "<%= config[:test] %>", "~> <%= config[:test_framework_version] %>"
 <%- end -%>
+
 <%- if config[:rubocop] -%>
 gem "rubocop", "~> 0.80"
 <%- end -%>

bundler/lib/bundler/templates/newgem/Rakefile.tt

@@ -36,4 +36,8 @@ Rake::ExtensionTask.new("<%= config[:underscored_name] %>") do |ext|
 end
 
 <% end -%>
-task default: <%= default_task_names.size == 1 ? default_task_names.first.inspect : default_task_names.inspect %>
+<% if default_task_names.size == 1 -%>
+task default: <%= default_task_names.first.inspect %>
+<% else -%>
+task default: %i[<%= default_task_names.join(" ") %>]
+<% end -%>

bundler/lib/bundler/templates/newgem/ext/newgem/extconf.rb.tt

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "mkmf"
 
 create_makefile(<%= config[:makefile_path].inspect %>)

bundler/lib/bundler/templates/newgem/test/minitest/newgem_test.rb.tt

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "test_helper"
 
 class <%= config[:constant_name] %>Test < Minitest::Test

bundler/lib/bundler/templates/newgem/test/minitest/test_helper.rb.tt

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 $LOAD_PATH.unshift File.expand_path("../lib", __dir__)
 require "<%= config[:namespaced_path] %>"
 

bundler/lib/bundler/templates/newgem/test/test-unit/newgem_test.rb.tt

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "test_helper"
 
 class <%= config[:constant_name] %>Test < Test::Unit::TestCase

bundler/lib/bundler/templates/newgem/test/test-unit/test_helper.rb.tt

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 $LOAD_PATH.unshift File.expand_path("../lib", __dir__)
 require "<%= config[:namespaced_path] %>"