Upgrade to faraday-multipart 1.2.0 for supports Ruby 4

[gemitoytp]

Hi there,

I'm running into a dependency conflict on Rails 8.1 / Ruby 4.0.0. It seems this gem currently pins faraday-multipart to 1.1.0, which doesn't support Ruby 4.0.0. Could you update the gemspec to allow version 1.2.0? It was recently released to address this exact compatibility issue.

Regards!