docs: Describe workaround for mysterious iOS upload failure.
docs: Describe workaround for mysterious iOS upload failure.

Still don't know why this happened, but nor do many of the people
discussing it on the Internet.  Glad this workaround worked.

Also connect this step to the previous one a bit better.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile