gitlab: drop HWLOC_COMPONENTS=x86

Problem: per the hwloc(7) documentation for hwloc v2.3.0, the
HWLOC_COMPONENTS environment variable, if used, will override
the HWLOC_XMLFILE variable. According to the docs, "since this
variable is the low-level and more generic way to select components,
it takes precedence over environment variables for selecting components."

I don't believe we've actually hit this problem. But just in case,
it seems advisable to drop the HWLOC_COMPONENTS variable in favor of
using the xml file.

.gitlab/machines.gitlab-ci.yml

@@ -14,29 +14,25 @@
         - corona
         - batch
     variables:
-        HWLOC_COMPONENTS: "x86"
         LLNL_FLUX_SCHEDULER_PARAMETERS: "--exclusive -N 1 -q pdebug --setattr=bank=lc"
 
 .poodle:
     tags:
         - poodle
         - batch
     variables:
-        HWLOC_COMPONENTS: "x86"
         LLNL_SLURM_SCHEDULER_PARAMETERS: "--exclusive -N 1 -p pdebug"
 
 .tioga:
     tags:
         - tioga
         - batch
     variables:
-        HWLOC_COMPONENTS: "x86"
         LLNL_FLUX_SCHEDULER_PARAMETERS: "--exclusive -N 1 -q pci"
 
 .quartz:
     tags:
         - quartz
         - batch
     variables: 
-        HWLOC_COMPONENTS: "x86"
         LLNL_SLURM_SCHEDULER_PARAMETERS: "-N 1 -p pdebug"