ref(minimal): Simplify syntheticException creation

[Turbo87]

Whether the error is thrown or not does not matter because stacktraces are generated when new Error() is called. In other words: the try-catch in captureException() and captureMessage() is unnecessary, and we can assign the new Error instance directly.

You can verify this by running the following snippet somewhere in your code:

let e = new Error('bla');
console.log(e);

try {
  throw new Error('bla');
} catch (error) {
  console.log(error);
}

Before submitting a pull request, please take a look at our Contributing guidelines and verify:

• If you've added code that should be tested, please add tests.
• Ensure your code lints and the test suite passes (yarn lint) & (yarn test).

[kamilogorek]

This branch of code is now 6 years old, and it comes from the ancient raven-js. I believe oooold old browsers did not create the stack when creating the Error object, thus this solution - #582
But I think it should be fine in the present times.

[lobsterkatie]

Nice.