Revert^2 "CMK-34961: update rustls-webpki to 0.103.15"

This reverts commit 4297dcf910ed025ff46e16e58a00600228123465.

Reason for revert: The initially reverted change uncovered a temporary infrastructure failure (AIX machine had no outbound internet access), that is resolved now.

Change-Id: I2f32ddd1ccc29c2f4f971caf41ad82f5efb8e9de