Speed up SAASBO tutorial by reducing dimension in smoke-test mode (#2463

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Summary:
Pull Request resolved: #2463

Context: This was taking too long to run.

This PR:
* Uses a 2d problem in smoke-test mode, cutting the runtime each of the two slowest cells by ~50%
* Uses LogEI instead of EI, getting rid of a warning

Differential Revision: D61083720