upload-release: Avoid appending to bytes in a loop.
upload-release: Avoid appending to bytes in a loop.

Appending to bytes in a loop leads to a quadratic slowdown since
Python doesn’t optimize this for bytes like it does for str.

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulip.com>

kou/zulip,andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,zulip/zulip,kou/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip