The encoder is sensitive to changes in precision, and its test target
was a compromise. It was already close to failing on x87 FPUs.
ff_mdct_init used double precision entirely from the scale to computing
the MDCT exp tables. av_tx_init uses single-precision for the scale,
with a small input change which was enough to tip the test into failing on
x87 FPUs.

Increase the fuzz factor in line with other AAC encoder tests to fix.