Change threaded fates test from `P32x2` to `P36x2`

[glemieux]

The current fates test ERP_D_P32x2_Ld3.f19_g17.I2000Clm50FatesCru.clm-FatesColdDef currently under utilizes the number of cores for Cheyenne (36 per node). For efficiency's sake we should increase the count to P36x2. This issue could be considered complimentary to #1736.

Additionally, in the course of addressing NGEET/fates#861 (comment), I found that running the following test case:

SMS_Ld3_P32x2.f45_f45_mg37.I2000Clm51FatesSpCruRsGs.cheyenne_intel.clm-FatesColdDefReducedComplexSatPhen

appears to get stuck and will timeout. Varying the test case parameters (duration, type, etc) clearly showed that the P32x2 modifier was at fault. Changing to a P36x2 test case resulted in the test completing in a reasonable time. The P32x2 case can be found here:

/glade/u/home/glemieux/scratch/ctsm-tests/tests_issue861-threaded-32x2

[glemieux]

This is planned to be incorporated in NGEET/fates#862 and #1766