Disable some tests on Dev17.0 branch

[KevinRansom]

These tests are failing on release/dev17.0 with with VS 16.10.3
Something changed we don't know what.

• Failed Regression.NoError.Timestamps.Bug3368b
• Regression.ModulesFromExternalLibrariesBug5785

We need to understand why, and ensure these tests execute.

[dsyme]

I think @TIHan put in a fix for these into main, I think it's #11731

[TIHan]

That fix doesn't resolve those tests. However, in main, we disabled both tests. I'm not convinced the tests are reliable and do the right thing; meaning the tests failing may not represent a symptom.