chore(transactions): remove unused code

Author: mbroadst

lib/transactions.js

@@ -107,10 +107,6 @@ class Transaction {
  this._recoveryToken = undefined;
  }
 
- get isPinned() {
- return this._pinnedServer != null;
- }
-
  get server() {
  return this._pinnedServer;
  }
@@ -149,10 +145,6 @@ class Transaction {
  );
  }
 
- get isPinned() {
- return this._pinnedServer != null;
- }
-
  pinServer(server) {
  if (this.isActive) {
  this._pinnedServer = server;