By Dan Levine SAN FRANCISCO (Reuters) – Witnesses at an upcoming trial over no-hire agreements in Silicon Valley should not be allowed to offer evidence that Apple co-founder Steve Jobs was a bully, four major tech companies argued in a court filing. Tech workers filed a class action lawsuit against Apple Inc, Google Inc, Intel Inc and Adobe Systems Inc in 2011, alleging they conspired to avoid competing for each others employees in order to avert a salary war. …