Bump hashicorp/google from 6.1.0 to 6.12.0

[roger2hk]

Towards #53.

The default_backup_schedule_type field was added to google_spanner_instance in 6.12.0.

https://github.com/hashicorp/terraform-provider-google/blob/main/CHANGELOG.md#6120-november-18-2024

17:57:08.912 INFO   Downloading Terraform configurations from ../../../modules/gcp into ./.terragrunt-cache/u2H3Rb8M2bUxoFwdXNwSqfaO1X4/u3yEPTHI42lFP2ufEiajjQcTgw0
17:57:10.772 STDERR terraform: ╷
17:57:10.772 STDERR terraform: │ Error: Unsupported argument
17:57:10.772 STDERR terraform: │ 
17:57:10.772 STDERR terraform: │   on ../storage/main.tf line 49, in resource "google_spanner_instance" "log_spanner":
17:57:10.772 STDERR terraform: │   49:   default_backup_schedule_type = "NONE"
17:57:10.773 STDERR terraform: │ 
17:57:10.773 STDERR terraform: │ An argument named "default_backup_schedule_type" is not expected here.
17:57:10.773 STDERR terraform: ╵
17:57:10.779 ERROR  terraform invocation failed in ./.terragrunt-cache/u2H3Rb8M2bUxoFwdXNwSqfaO1X4/u3yEPTHI42lFP2ufEiajjQcTgw0/conformance
17:57:10.779 ERROR  error occurred:

* Failed to execute "terraform plan" in ./.terragrunt-cache/u2H3Rb8M2bUxoFwdXNwSqfaO1X4/u3yEPTHI42lFP2ufEiajjQcTgw0/conformance
  ╷
  │ Error: Unsupported argument
  │ 
  │   on ../storage/main.tf line 49, in resource "google_spanner_instance" "log_spanner":
  │   49:   default_backup_schedule_type = "NONE"
  │ 
  │ An argument named "default_backup_schedule_type" is not expected here.
  ╵
  
  exit status 1