style: Capitalise Terraform where product name is meant

[mloskot]

The Hashicorp's product name is Terraform, similarly to OpenTofu and not opentofu.

This also distinguishes command-line terraform from Terraform product.

[github-actions]

Terraform plan for pull_request_target

Plan: 1 to add, 0 to change, 0 to destroy. Changes to Outputs.

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
+   create

Terraform will perform the following actions:

  # random_string.my_string will be created
+   resource "random_string" "my_string" {
+       id          = (known after apply)
+       length      = 11
+       lower       = true
+       min_lower   = 0
+       min_numeric = 0
+       min_special = 0
+       min_upper   = 0
+       number      = true
+       numeric     = true
+       result      = (known after apply)
+       special     = true
+       upper       = true
    }

Plan: 1 to add, 0 to change, 0 to destroy.

Changes to Outputs:
+   output_string = "the_string"

✅ Plan applied in pull_request_target test #613

Outputs

output_string = "the_string"