Cut back on error messages

[jonathanmetzman]

We get quite a few error messages from this line of code: https://github.com/google/clusterfuzz/blob/9edf0ba19e5ece0105cee1cf8c018f39b66a67ec/src/clusterfuzz/_internal/datastore/data_handler.py#L815

Such as:

Crash occurs, but not too consistently. Skipping minimization (crashed 4/10)
Testcase appears to be flaky (testcase 6284147979649024, job linux_asan_chrome_mp).
Unable to reproduce crash (testcase 6284147979649024, job linux_asan_chrome_mp

I think most of these especially the last one should not be logged as errors since they don't mean our infra is broken. What do you think of me deleting this behavior? @oliverchang