Fix output of non-reader sources for Catalyst Python scripts

When outputting Catalyst Python scripts for the new export mechanism
non-reader sources were incorrectly being output as Catalyst
inputs/channels. Fixed to properly recognize that they are other
available sources.

Fixes: #18558
25 jobs for fix_catalyst_source_output
Status Job ID Name Coverage
  External
passed cdash

passed ghostflow-branch-check-master

pending paraview@master-dres-osx-shared-release+gui+python2
pending paraview@master-luigi-linux-shared-release+gui+mpi+python2
failed paraview@master-nemesis-windows-shared-release+gui+kits+mpi+python2

passed paraview@master-taanab-linux-shared-release+mpi+python2

passed paraview@master-taanab-linux-static-release+mpi+offscreen+osmesa+python2

failed paraview@master-tylo-windows-shared-release+gui+python3+tbb

running paraview@master-vall-linux-shared-debug+doc+extdeps+gui+mpi+python3

4747:38:43

failed paraview@master-nemesis-windows-shared-release+gui+kits+mpi+python2

failed paraview@master-nemesis-windows-shared-release+gui+kits+mpi+python2

failed paraview@master-nemesis-windows-shared-release+gui+kits+mpi+python2

failed paraview@master-nemesis-windows-shared-release+gui+kits+mpi+python2

00:47:04

passed paraview@master-taanab-linux-shared-release+mpi+python2

00:03:54

passed paraview@master-taanab-linux-shared-release+mpi+python2

passed paraview@master-taanab-linux-shared-release+mpi+python2

passed paraview@master-taanab-linux-shared-release+mpi+python2

passed paraview@master-taanab-linux-static-release+mpi+offscreen+osmesa+python2

passed paraview@master-taanab-linux-static-release+mpi+offscreen+osmesa+python2

passed paraview@master-taanab-linux-static-release+mpi+offscreen+osmesa+python2

passed paraview@master-taanab-linux-static-release+mpi+offscreen+osmesa+python2

00:02:54

failed paraview@master-tylo-windows-shared-release+gui+python3+tbb

failed paraview@master-tylo-windows-shared-release+gui+python3+tbb

failed paraview@master-tylo-windows-shared-release+gui+python3+tbb

failed paraview@master-tylo-windows-shared-release+gui+python3+tbb

00:47:17