switch repo fork for the websocket package

The `michaelsbradleyjr/Websocket-Node#polyfill/globalThis` branch uses a more
robust approach to resolve a browser's `window` object. It also includes all
the latest commits on the upstream's `master` branch, including fixes for the
`.git/` subdir npm bug and Node v12.x compatibility.

The `"preinstall"` script in `packages/web3-providers-ws/package.json` is
removed because it's not helpful and its use of `rm` causes Windows
incompatibility. Closes #2971 and #2973.

`packages/web3-providers-ws/src/index.js` is refactored since the `websocket`
package already does native WebSocket detection.

Author: michaelsbradleyjr

dist/web3.min.js

@@ -12,7 +12,7 @@ if (isNode) {
     var tryScryptPkg = (function() {
         var scryptPkg;
         return function() {
-            if (scryptPkg !== undefined) { return scryptPkg; };
+            if (scryptPkg !== undefined) { return scryptPkg; }
             try {
                 scryptPkg = (function(m) { return require(m); })('scrypt');
             } catch (e) {