PbsproScheduler: Replace deprecated ppn tag with ncpus (#5910)

The `PbsproScheduler` was using the tag `ppn` to define the number of
cores per machine to request. This notation was deprecated at least as
of v13 of PBSPro and has recently been removed entirely. It is removed
in favor of `ncpus`.

aiida/schedulers/plugins/pbspro.py

@@ -66,7 +66,7 @@ def _get_resource_lines(
         if num_mpiprocs_per_machine:
             select_string += f':mpiprocs={num_mpiprocs_per_machine}'
         if num_cores_per_machine:
-            select_string += f':ppn={num_cores_per_machine}'
+            select_string += f':ncpus={num_cores_per_machine}'
 
         if max_wallclock_seconds is not None:
             try:

tests/schedulers/test_pbspro.py

@@ -1008,7 +1008,7 @@ def test_submit_script_with_num_cores_per_mpiproc(self):
         self.assertTrue('#PBS -r n' in submit_script_text)
         self.assertTrue(submit_script_text.startswith('#!/bin/bash'))
 
-        self.assertTrue('#PBS -l select=1:mpiprocs=1:ppn=24' in submit_script_text)
+        self.assertTrue('#PBS -l select=1:mpiprocs=1:ncpus=24' in submit_script_text)
         # Note: here 'num_cores_per_machine' should NOT override the mpiprocs
 
         self.assertTrue("'mpirun' '-np' '23' 'pw.x' '-npool' '1' < 'aiida.in'" in submit_script_text)
@@ -1042,7 +1042,7 @@ def test_submit_script_with_num_cores_per_machine_and_mpiproc1(self):
 
         self.assertTrue('#PBS -r n' in submit_script_text)
         self.assertTrue(submit_script_text.startswith('#!/bin/bash'))
-        self.assertTrue('#PBS -l select=1:mpiprocs=1:ppn=24' in submit_script_text)
+        self.assertTrue('#PBS -l select=1:mpiprocs=1:ncpus=24' in submit_script_text)
         # Note: here 'num_cores_per_machine' should NOT override the mpiprocs
 
         self.assertTrue("'mpirun' '-np' '23' 'pw.x' '-npool' '1' < 'aiida.in'" in submit_script_text)