Update PMIx submodule pointer to latest v4.2.

Commits since last update:

be2a27d6 - Return "succeeded" status when outputting help/version info
a3216718 - Fix pcompress/zlib implementation (open-mpi#2625)
84e1c231 - Fix typos.
3edfda51 - Add PMIx Standard version info to pmix_info
32ff1b03 - Update the PMIx ABI Query attributes to match the standard
45eaba22 - Add examples for using PMIx_Query_info with PMIX_QUERY_ABI_VERSION
a978d02e - Backend query support for PMIX_QUERY_ABI_VERSION and local keys
52803578 - Setup PMIX_STD_ABI_VERSION in the VERSION file
7cbe9b67 - Fix the greek version

Signed-off-by: Austen Lauria <[email protected]>

Author: awlauria