[Pillow] Removed zlib1g-dev installation

[radarhere]

Pillow recently started building zlib on Linux in it's wheels, and that is conflicting with the installation of zlib1g-dev from our oss-fuzz Dockerfile.

./.libs/libpng16.so: undefined reference to `inflateValidate'

Copying files from here as a test, it fails with the same error, and then with this PR, it ... well, it doesn't pass exactly, but it makes it to "FUZZING_LANGUAGE: unbound variable", which I presume is just an artefact of my testing setup.

So this PR removes zlib1g-dev from the list of apt-get installations.

cc @wiredfool

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[radarhere]

@googlebot I signed it!

[DavidKorczynski]

LGTM. The issues with the CI is unrelated to Pillow. I have checked the build passes locally.

[DavidKorczynski]

@jonathanmetzman this one is good to get merged in - the CI currently fails due to the issue where additional projects gets build in the CI (in this case freeradius) which fail.