Bug#1148924: test failure due to stderr warning schizo_proxy deprecated by personality

[Drew Parsons]

Source: openmpi
Followup-For: Bug #1148924
Control: severity -1 serious

As far as I can tell, the offending line of code is
https://salsa.debian.org/hpc-team/openmpi/-/blob/debian/latest/ompi/tools/mpirun/main.c?ref_type=heads#L137

 setenv("PRTE_MCA_schizo_proxy", "ompi", 1);
 
Upstream sets both (with PRTE_MCA_personality) "for compatibility with
older and newer PRRTE versions.".

But for the debian build we don't need this compatibility with older PRRTE
versions.

Bumping severity to serious, since this issue is blocking other
packages migrating to testing.