Remove the old TNNMGStep implementation

2 jobs for feature/new_tnnmg in 21 seconds (queued for 4 seconds)
Name Stage Failure
failed
dune:git--gcc Test There is an unknown failure, please try again
--- calling vcsetup for dune-solvers ---
--- calling configure for dune-solvers ---
ERROR: could not find module 'dune-matrix-vector',
module is also unknown to pkg-config.
Maybe you need to adjust PKG_CONFIG_PATH!
'dune-matrix-vector' is required by dune-solvers
--- Failed to build dune-solvers ---
Terminating dunecontrol due to previous errors!
ERROR: Build failed: exit code 1
failed
dune:git--clang Test There is an unknown failure, please try again
--- calling vcsetup for dune-solvers ---
--- calling configure for dune-solvers ---
ERROR: could not find module 'dune-matrix-vector',
module is also unknown to pkg-config.
Maybe you need to adjust PKG_CONFIG_PATH!
'dune-matrix-vector' is required by dune-solvers
--- Failed to build dune-solvers ---
Terminating dunecontrol due to previous errors!
ERROR: Build failed: exit code 1