feat: remove deprecated v4 string parameter (#454)

In version 1.x of this library it was possible to call `v4('binary')` in
order to receive a byte array instead of a string representation. This
function signature was deprecated in 2.x (but not removed in 3.x as it
should have been).

The correct way to get a binary representation of a uuid is to pass an
array-like object as a second parameter:

```
const buffer = new Array();
v4(null, buffer);
```

Fixes #437.

src/v4.js

@@ -2,11 +2,6 @@ import rng from './rng.js';
 import bytesToUuid from './bytesToUuid.js';
 
 function v4(options, buf, offset) {
-  if (typeof options === 'string') {
-    buf = options === 'binary' ? new Uint8Array(16) : null;
-    options = null;
-  }
-
   options = options || {};
 
   const rnds = options.random || (options.rng || rng)();