Resolve "Romeo SMT enabled by default?"

Closes #476 (closed)

To get 256 cores per node --hint=multithread has to be specified or SLURM returns salloc: error: Job submit/allocate failed: Requested node configuration is not available This shows SMT is diabled per default and has to be enabled by the user

Furthermore I added a note how to activate SMT on alpha partition similar to romeo

doc.zih.tu-dresden.de/docs/jobs_and_resources/alpha_centauri.md

@@ -12,6 +12,15 @@ The hardware specification is documented on the page
     The NVIDIA A100 GPUs may only be used with **CUDA 11** or later. Earlier versions do not
     recognize the new hardware properly. Make sure the software you are using is built with CUDA11.
 
+There is a total of 48 physical cores in each node. SMT is also active, so in total, 96 logical
+cores are available per node.
+
+!!! note
+
+    Multithreading is disabled per default in a job. To make use of it include the Slurm parameter
+    `--hint=multithread` in your job script or command line, or set the environment variable
+    `SLURM_HINT=multithread` before job submission.
+
 ### Modules
 
 The easiest way is using the [module system](../software/modules.md).