Revert "feat(Update): add the ability to specify a pipeline to an update command (#2017)"

This reverts commit 44a4110.

Author: daprahamian

lib/collection.js

@@ -697,15 +697,7 @@ Collection.prototype.updateOne = function(filter, update, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
   options = options || {};
 
-  let err;
-  if (Array.isArray(update)) {
-    for (let i = 0; !err && i < update.length; i++) {
-      err = checkForAtomicOperators(update[i]);
-    }
-  } else {
-    err = checkForAtomicOperators(update);
-  }
-
+  const err = checkForAtomicOperators(update);
   if (err) {
     if (typeof callback === 'function') return callback(err);
     return this.s.promiseLibrary.reject(err);