dev-cmd: enable frozen string literals

Now that we use Ruby 2.6 we can fix these last two files.

Library/Homebrew/dev-cmd/bottle.rb

@@ -1,6 +1,4 @@
-# Uses ERB so can't use Frozen String Literals until >=Ruby 2.4:
-# https://bugs.ruby-lang.org/issues/12031
-# frozen_string_literal: false
+# frozen_string_literal: true
 
 require "formula"
 require "utils/bottles"
@@ -11,7 +9,7 @@ require "cli/parser"
 require "utils/inreplace"
 require "erb"
 
-BOTTLE_ERB = <<-EOS.freeze
+BOTTLE_ERB = <<-EOS
   bottle do
     <% if  !root_url.start_with?(HOMEBREW_BOTTLE_DEFAULT_DOMAIN) %>
     root_url "<%= root_url %>"
@@ -43,7 +41,7 @@ module Homebrew
 
   def bottle_args
     Homebrew::CLI::Parser.new do
-      usage_banner <<~EOS.freeze
+      usage_banner <<~EOS
         `bottle` [<options>] <formula>
 
         Generate a bottle (binary package) from a formula that was installed with
@@ -382,7 +380,7 @@ module Homebrew
           "#{key}: old: #{old_value}, new: #{value}"
         end
 
-        odie <<~EOS.freeze
+        odie <<~EOS
           --keep-old was passed but there are changes in:
           #{mismatches.join("\n")}
         EOS
@@ -493,7 +491,7 @@ module Homebrew
               end
 
               unless mismatches.empty?
-                odie <<~EOS.freeze
+                odie <<~EOS
                   --keep-old was passed but there are changes in:
                   #{mismatches.join("\n")}
                 EOS

Library/Homebrew/dev-cmd/man.rb

@@ -1,6 +1,4 @@
-# Uses ERB so can't use Frozen String Literals until >=Ruby 2.4:
-# https://bugs.ruby-lang.org/issues/12031
-# frozen_string_literal: false
+# frozen_string_literal: true
 
 require "formula"
 require "erb"
@@ -18,7 +16,7 @@ module Homebrew
 
   def man_args
     Homebrew::CLI::Parser.new do
-      usage_banner <<~EOS.freeze
+      usage_banner <<~EOS
         `man` [<options>]
 
         Generate Homebrew's manpages.