Update py-mutagen to 1.45.1, needed for PR pkg/56378.

1.45.1 - 2020-07-31

Fix flake8 tests when run after calling setup.py build
No longer use mmap when rewriting files. Fixes slow save performance with
Windows network shares, ZFS and more

1.45.0 - 2020-07-11

WAVE support with ID3 tags
DSDIFF support with ID3 tags
MP4: Add support for nero chapters
wavpack: add support for wavpack DSD
wavpack: add bits_per_sample
MP4: handle DecoderSpecificInfo with wrong instance size
docs: various fixes
tests: depend on flake8 now (instead of pycodestyle and pyflakes)
docs: fix warnings with sphinx v3

Fuzzing related:
Fuzzing integration with python-afl
Fix various unhandled error cases in ogg, asf, oggvorbis, id3
aac: Fix ZeroDivisionError in case frequency is unknown
musepack: handle truncated stream header
musepack: handle invalid sample rate index
musepack: handle duplicate RG/SH packets
oggtheora: handle truncated header packet
oggtheora: fail if FRN in the header packet is zero
oggtheora: handle empty pages in more cases
ogg: handle empty pages in to_packets()
aiff: handle overflow in read_float()

(bsiegert)