feature: support local option for terraform (#96)

# Pull Request

## Issue

Issue #, if available:
https://github.com/Azure/alz-terraform-accelerator/issues/69

## Description

This removes the validation on the CI / CD variable for Terraform (Bicep
retains it).

This is to support additional bootstrap types without needing to make
changes to this module moving forwards.

## License

By submitting this pull request, I confirm that my contribution is made
under the terms of the projects associated license.

Author: jaredfholgate

src/ALZ/Private/New-ALZEnvironmentTerraform.ps1

@@ -11,7 +11,6 @@ function New-ALZEnvironmentTerraform {
         [string] $alzVersion,
 
         [Parameter(Mandatory = $false)]
-        [ValidateSet("github", "azuredevops")]
         [Alias("Cicd")]
         [string] $alzCicdPlatform,
 

src/ALZ/Public/New-ALZEnvironment.ps1

@@ -48,7 +48,6 @@ function New-ALZEnvironment {
         [string] $alzIacProvider = "bicep",
 
         [Parameter(Mandatory = $false)]
-        [ValidateSet("github", "azuredevops")]
         [Alias("Cicd")]
         [Alias("c")]
         [string] $alzCicdPlatform = "github",