fix: webhook expects REPOSITORY_ALLOW_LIST env var (#3856)

#### Description

The `ConfigResolver` of the webhook lambda expects the env variable to
be named `REPOSITORY_ALLOW_LIST` (see
https://github.com/philips-labs/terraform-aws-github-runner/blob/1e40ecda859e961679f80a16135e23e9d8e4a2dd/lambdas/functions/webhook/src/ConfigResolver.ts#L18)
whereas the one set by the `webhook` module was `REPOSITORY_WHITE_LIST`.
I think it'd be great to follow up on
https://github.com/philips-labs/terraform-aws-github-runner/issues/992,
but it is beyond the scope of the fix proposed here now.

Author: galargh

modules/webhook/webhook.tf

@@ -29,7 +29,7 @@ resource "aws_lambda_function" "webhook" {
       POWERTOOLS_TRACER_CAPTURE_HTTPS_REQUESTS = var.tracing_config.capture_http_requests
       POWERTOOLS_TRACER_CAPTURE_ERROR          = var.tracing_config.capture_error
       PARAMETER_GITHUB_APP_WEBHOOK_SECRET      = var.github_app_parameters.webhook_secret.name
-      REPOSITORY_WHITE_LIST                    = jsonencode(var.repository_white_list)
+      REPOSITORY_ALLOW_LIST                    = jsonencode(var.repository_white_list)
       SQS_WORKFLOW_JOB_QUEUE                   = try(var.sqs_workflow_job_queue, null) != null ? var.sqs_workflow_job_queue.id : ""
       PARAMETER_RUNNER_MATCHER_CONFIG_PATH     = aws_ssm_parameter.runner_matcher_config.name
     }