Move "quiet" configuration to an environment var

The JS based one does not appear to silence all tips.

Author: desrosj

.env.example

@@ -67,3 +67,8 @@ LOCAL_WP_TESTS_DOMAIN=example.org
 
 # The URL to use when running e2e tests.
 WP_BASE_URL=http://localhost:${LOCAL_PORT}
+
+##
+# This silences the tips output by the dotenv package.
+##
+DOTENV_CONFIG_QUIET=true

tools/local-env/scripts/start.js

@@ -1,6 +1,6 @@
 /* jshint node:true */
 
-const dotenv       = require( 'dotenv' ).config({ quiet: true });
+const dotenv       = require( 'dotenv' );
 const dotenvExpand = require( 'dotenv-expand' );
 const { execSync, spawnSync } = require( 'child_process' );
 const local_env_utils = require( './utils' );