DAOS-18991 test: Remove python3-mpi4py-tests requirement

[phender]

Remove python3-mpi4py-tests to avoid conflict with pip install of mpi4py

Skip-unit-tests: true
Skip-fault-injection-test: true
Test-tag: LlnlMpi4py

Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[daosbuild3]

Test stage Functional on EL 9 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18330/2/testReport/

[github-actions]

Ticket title is 'mpiio/llnl_mpi4py.py:LlnlMpi4py.test_mpi4py - libmpi.so: cannot open shared object file: No such file or directory on Leap15.6'
Status is 'Open'
Labels: 'ci_master_daily'
https://daosio.atlassian.net/browse/DAOS-18991

[daosbuild3]

Test stage Functional on EL 8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18330/2/testReport/

[daosbuild3]

Test stage Functional on SLES 15 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18330/2/testReport/

[daosbuild3]

Test stage Functional on Leap 15 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18330/2/testReport/