[clang][RelativeVTablesABI] Update CodeGenCXX/RelativeVTablesABI/dynamic-cast.cpp

After c7bcd431, this test started failing when
running with the new pass manager. One of the CHECKs in this file checks how the
vtable is loaded for a void cast, which involves taking 2 bitcasts from the pointer
to the original object. The order of these bitcasts changes under the new PM.
The order doesn't matter, so this relaxes the CHECKs.

Differential Revision: https://reviews.llvm.org/D82802