Correct AssignMasterSlaveConstraintsToNeighboursProcess and Remove Trailing Spaces

[SADPR]

Description:

This pull request addresses a correction in the AssignMasterSlaveConstraintsToNeighboursProcess. The previous implementation contained an error where the self.variables_list was being looped over and passed individually to the AssignMasterSlaveConstraintsToNodes method when self.reform_constraints_at_each_step was False. This was incorrect as the entire self.variables_list should be passed as a parameter to the AssignMasterSlaveConstraintsToNodes method.

Changes:

Correct the AssignMasterSlaveConstraintsToNeighboursProcess by passing the entire self.variables_list as a parameter to the AssignMasterSlaveConstraintsToNodes method when self.reform_constraints_at_each_step is False.

# Before
if not self.reform_constraints_at_each_step:
    for variable in self.variables_list:
        self.assign_mscs_utility.AssignMasterSlaveConstraintsToNodes(self.slave_model_part.Nodes,self.search_radius,self.computing_model_part, variable, self.minimum_number_of_neighbouring_nodes)

# After
if not self.reform_constraints_at_each_step:
    self.assign_mscs_utility.AssignMasterSlaveConstraintsToNodes(self.slave_model_part.Nodes,self.search_radius,self.computing_model_part, self.variables_list, self.minimum_number_of_neighbouring_nodes)

Also: Removed trailing spaces in the modified files for a cleaner codebase.