message: Fixes how we specify the desired spack commit in project.json
  We were using the wrong keyword for this and uberenv was ignoring it.
  As a consequence, we were building our TPLs against spack's develop branch.
  We are now using the correct keyword: 'spack_commit'
diff: {
  "package_name" : "axom",
  "uberenv_package_name" : "uberenv-axom",
  -"spack_develop_commit": "729bed3fd3e7bd3ecabda3ab25525019f3f83661",
  +"spack_commit": "729bed3fd3e7bd3ecabda3ab25525019f3f83661",
  "spack_activate" : {"py-breathe": ["+devtools"],
  "py-sphinx" : ["+devtools"],
  "py-shroud" : ["+devtools"],
  