feat: upgrade SOPS to v3.12.1

[putsuka]

Summary

Upgrade getsops/sops from v3.10.2 to v3.12.1.

Motivation

This upgrade brings several improvements and bug fixes from SOPS, including support for
selecting GCP KMS client type via the SOPS_GCP_KMS_CLIENT_TYPE environment variable
(getsops/sops#1973). This helps avoid timeout errors when operating through a VPN or HTTP proxy.

Changes

• Update github.com/getsops/sops/v3 from v3.10.2 to v3.12.1
• Update related dependencies

Backward Compatibility

Fully backward compatible. No breaking changes.

[putsuka]

Hi @carlpett
This PR upgrades SOPS to v3.12.1. I'd appreciate it if you could review this when you have time.
Thank you!

[carlpett]

Thanks!

[putsuka]

Hi @carlpett,

Thank you for merging PR #150! Could you please cut a new release tag when you get a chance?

Thank you!