Update --env-file documentation when a file cannot be found.

[arthurfiorette]

Node.js runs normally when the env file cannot be found. I think this behavior is good to be documented.

echo 'console.log(process.env)' > test.js;
echo 'A=1' > .env;

# does not prints A: '1'
node --env-file=not-found-env-file.env test.js;
node --env-file=not-found-env-file.env -e 'console.log(process.env)';

# prints A: '1'
node --env-file=.env test.js;
node --env-file=.env test.js -e 'console.log(process.env)';

[anonrig]

This doesn't apply anymore. Ref: #50588