bpo-39356, zipfile: Remove code handling DeprecationWarning (GH-18027)

Remove old "except DeprecationWarning:" code path added by
commit bf02e3bb21b2d75cba4ce409a14ae64dbc2dd6d2. It's no longer
needed.

struct.pack() no longer emit DeprecationWarning if getting a float
whereas an integer is expected. It now raises an hard error instead.