Weaken checks for file size

The size given to dexter is the size of the buffer, not necessarily
the size of the data contained within it. We need to loosen some
checks to make dexter/slicer continue to work.

Bug: 72402467
Test: ./art/test.py --host --redefine-stress -j50
Change-Id: I1be810a641f877602a1848dace197d8a74c43341