Fix Layout/MultilineOperationIndentation offenses

```
rubocop --only Layout/MultilineOperationIndentation -a
```

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/axlsx/package.rb b/lib/axlsx/package.rb
index 5bd8d5c2..0c03b1a2 100644
--- a/lib/axlsx/package.rb
+++ b/lib/axlsx/package.rb
@@ -375,7 +375,7 @@ module Axlsx
     def parse_serialize_options(options, secondary_options)
       if secondary_options
         warn "[DEPRECATION] Axlsx::Package#serialize with 3 arguments is deprecated. " +
-          "Use keyword args instead e.g., package.serialize(output, confirm_valid: false, zip_command: 'zip')"
+             "Use keyword args instead e.g., package.serialize(output, confirm_valid: false, zip_command: 'zip')"
       end
       if options.is_a?(Hash)
         options.merge!(secondary_options || {})
@@ -386,7 +386,7 @@ module Axlsx
         [options.fetch(:confirm_valid, false), options.fetch(:zip_command, nil)]
       else
         warn "[DEPRECATION] Axlsx::Package#serialize with confirm_valid as a boolean is deprecated. " +
-          "Use keyword args instead e.g., package.serialize(output, confirm_valid: false)"
+             "Use keyword args instead e.g., package.serialize(output, confirm_valid: false)"
         parse_serialize_options((secondary_options || {}).merge(confirm_valid: options), nil)
       end
     end