[lyon] Fix ref. API for taurus-15 threads

data/grid5000/sites/lyon/clusters/taurus/nodes/taurus-15.json

@@ -2,7 +2,7 @@
   "architecture": {
     "platform_type": "x86_64",
     "smp_size": 2,
-    "smt_size": 24
+    "smt_size": 12
   },
   "bios": {
     "release_date": "05/10/2012",

generators/input/sites/lyon/clusters/taurus_generated.yaml

@@ -1393,7 +1393,7 @@ taurus-15:
   architecture:
     smp_size: 2
     platform_type: x86_64
-    smt_size: 24
+    smt_size: 12
 taurus-16:
   bios:
     version: 1.2.6