rubocop: fix Style/CollectionCompact

Library/Homebrew/system_command.rb

@@ -100,12 +100,11 @@ class SystemCommand
   end
 
   def env_args
-    set_variables = env.reject { |_, value| value.nil? }
-                       .map do |name, value|
-                         sanitized_name = Shellwords.escape(name)
-                         sanitized_value = Shellwords.escape(value)
-                         "#{sanitized_name}=#{sanitized_value}"
-                       end
+    set_variables = env.compact.map do |name, value|
+      sanitized_name = Shellwords.escape(name)
+      sanitized_value = Shellwords.escape(value)
+      "#{sanitized_name}=#{sanitized_value}"
+    end
 
     return [] if set_variables.empty?