static-delta: Drop unreliable usize-based margin heuristic

static-delta: Drop unreliable usize-based margin heuristic

The per-object margin formula added in the previous commit tries to
bound the gap between a delta part's declared usize (sum of
reconstructed object sizes) and its actual decompressed payload size
by scaling with the number of objects in the part.  That's the wrong
axis: the biggest source of that gap is the bsdiff patch stream for
bsdiff'd objects, which scales with object *content* size, not object
*count*.  A part with just one or two large bsdiff'd objects (e.g. a
big shared library that changed significantly between releases) blows
right past the margin, causing legitimate deltas to be rejected at
apply time.  This is the root cause of
https://github.com/ostreedev/ostree/issues/3635.

Just drop it, we'll work to add a more reliable limit later.

Assisted-by: https://github.com/cgwalters/cgwalters#llms
Signed-off-by: Colin Walters <walters@verbum.org>