fix: ensure BodyPartReader.read() returns bytes, not bytearray #16590

Job	Run time
Linter	52s
Generate llhttp sources	7s
Pre-Setup global build settings	2s
Benchmark	11m 34s
Autobahn testsuite (3.14, ubuntu)	10m 3s
Cython coverage (ubuntu)	2m 4s
Cython coverage (windows)	4m 13s
Test (3.11, ubuntu, false)	4m 21s
Test (3.10, ubuntu, false)	4m 48s
Test (3.10, macos, false)	6m 58s
Test (3.11, macos, false)	5m 56s
Test (3.10, windows, false)	5m 58s
Test (3.11, Y, ubuntu, false)	5m 11s
Test (3.14, ubuntu, false)	4m 45s
Test (3.10, Y, ubuntu, false)	5m 48s
Test (3.13, ubuntu, false)	4m 20s
Test (3.13, macos, false)	6m 30s
Test (3.13, Y, ubuntu, false)	5m 35s
Test (3.12, windows, false)	6m 26s
Test (3.12, ubuntu, false)	4m 28s
Test (3.11, windows, false)	5m 46s
Test (3.12, Y, ubuntu, false)	5m 27s
Test (3.14, macos, false)	7m 26s
Test (3.13, windows, false)	5m 46s
Test (ubuntu, 3.14t, false)	3m 56s
Test (3.14, Y, ubuntu, false)	5m 59s
Test (3.14, windows, false)	7m 10s
Test (pypy-3.11, Y, ubuntu, false)	9m 48s
Test (3.12, macos, false)	5m 51s
check	6s
Pre-Deploy	0s
Tarball	0s
Build wheels on ${{ matrix.os }} ${{ matrix.qemu }} ${{ matrix.musl }}	0s
Deploy	0s
	2h 37m 14s

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