[REFACTOR] Reduce walltime of examples

Currently, the examples are all searching for 5 minutes which I think for the datasets we use is too long. Especially for the purpose of demonstrating the functionality of AutoPyTorch, I think its a bit excessive. We should reduce it to 100 seconds for each search as this will also greatly reduce the time it takes to pass the `build-and-deploy` check for each PR. Its not urgent but it will be useful.