Support newer Google Cloud provider versions

[yu-iskw]

The supported Google Cloud provider version is less than 5.0. However, the latest major version of the google provider is 6.

terraform-google-cloud-workflows/versions.tf

Line 22 in c3af198

version = ">= 3.53, < 5.0"

  required_providers {
    google = {
      source  = "hashicorp/google"
      version = ">= 3.53, < 5.0"
    }