[IR] Remove getDestAlignment and getSourceAlignment (#151282)
This patch removes getDestAlignment and getSourceAlignment as they
have been deprecated for more than two years since:
commit 135f23d67bf5397745be1897afd0a3a50119089f
Author: Guillaume Chatelet <gchatelet@google.com>
Date: Mon Jan 16 12:34:40 2023 +0000
I'm not aware of any downstream users AFAIK.