Update comments for requirements for NEST Server (+ MPI)

requirements_nest_server.txt

@@ -1,15 +1,12 @@
 # Required Python packages to run NEST Server.
 #
-# This file specifies the required Python packages to run NEST Server.
-# It is meant for those who would like to compile NEST or build NEST
-# documentation themselves. If you just want to execute NEST, you should
-# install NEST directly as described in
-# https://www.nest-simulator.org/installation.
+# This file specifies the required Python packages to run NEST Server. It is meant for those who would like to compile
+# NEST or build NEST documentation themselves. If you just want to execute NEST, you should install NEST directly as
+# described in https://www.nest-simulator.org/installation.
 #
-# The listed requirements are used to build the conda environment defined
-# in the environment yaml file. If you want to build an environment
-# yourself, e.g., independent of conda, the requirements from this file
-# can be installed by
+# The listed requirements are used to build the conda environment defined in the environment yaml file. If you want to
+# run nest-server with mpi, please uncomment to install required packages. If you want to build an environment yourself,
+# e.g., independent of conda, the requirements from this file can be installed by
 #
 #     pip install -r requirements_nest_server.txt
 
@@ -19,6 +16,6 @@ gunicorn
 requests
 RestrictedPython
 
-# Packages for mpi
+# Uncomment next lines of packages for mpi:
 # docopt
 # mpi4py