fix: remove provider block in child module (#134)

## Motivation
The child module should not declare provider block, which will override
the root module.

Signed-off-by: Max Xu <xuhuan@live.cn>

Author: maxsxu

modules/aws/private-link/main.tf

@@ -1,7 +1,3 @@
-provider "aws" {
-  region = var.region
-}
-
 data "aws_vpc" "this" {
   id = var.vpc_id
 }