Remove erroneous which call from gen_xps_mod_ucf

The `which` function in matlab looks up the location of functions,
variables, models, java classes etc.  In `gen_xps_mod_ucf`, it was being
used in an apprarent attempt to lookup UCF files in a given directory,
but that is not an appropriate use of `which` and it is not necessary,
so the call to `which` was simply removed.

xps_library/gen_xps_mod_ucf.m

@@ -108,7 +108,7 @@ function gen_xps_mod_ucf(xsg_obj, xps_objs, mssge_proj, mssge_paths, slash)
             fprintf(ucf_fid,'##############################################\n');
 
             for n = 1:length(user_ucf_files)
-                file_path = which(fullfile(user_ucf_path, user_ucf_files(n).name));
+                file_path = fullfile(user_ucf_path, user_ucf_files(n).name);
                 fprintf(ucf_fid, '\n\n### BEGIN %s\n\n', file_path);
                 fprintf(ucf_fid, fileread(file_path));
                 fprintf(ucf_fid, '\n\n### END %s\n\n', file_path);