Update zlib fingerprint with zlib version 1.2.11.

I reviewed the code changes, there's no compression algorithm changes
except level 0 which imgdiff does not support (it only support level 6
and 9).

I also compressed a few files and compared the result with 1.2.8, and
the files are exactly the same.

Test: update_engine_unittests
Change-Id: Iedc3bf5e08c0d5431acb67f4180cf40a6b5012db