package/libjpeg: switch to s.b.o. as source site

package/libjpeg: switch to s.b.o. as source site

Fixes #13581

The tarball for version 9d, released 2020-01-12, has been silently
replaced upstream (a unicode BOM was removed from a few files),
causing hash mismatch.

This means that all our versions since 2020.02 will fail the hash
check, and fallback to using s.b.o. so we can't update the copy we
have on s.b.o.

As a consequence, we can't update the hash in master (soon 2021.02)
otherwise it would not match what we have on s.b.o.

This means that users will see hash mismatch by default, which is not
very nice. Although we can't do anything for all previous releases,
we can still try to paper over the problem for the future ones, like
2021.02, by switching the upstream to be s.b.o.

Sigh... :-(

Reported-by: Nick Shaforostov <mshaforostov@airmusictech.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>