Update Terraform provider syntax

Author: nchammas

test-infra/provider.tf

@@ -1,8 +1,16 @@
-provider "aws" {
-  version = "~> 2"
-  region  = "us-east-1"
+terraform {
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = "~> 2"
+    }
+    http = {
+      source  = "hashicorp/http"
+      version = "~> 1"
+    }
+  }
 }
 
-provider "http" {
-  version = "~> 1"
+provider "aws" {
+  region = "us-east-1"
 }