build(deps): bump google.golang.org/genai from 1.67.0 to 1.68.0 - #412

Failed to save: Unable to reserve cache with key setup-go-Linux-x64-ubuntu24-go-1.26.6-81c931f3e2432641cf0489633fb4478e84cb77a69e927633cff7e5614a4e332e. More details: cache write denied: token has no writable scopes