[common][fvproblem] add note to constructor without spatial params

5 jobs for !2839 with feature/base-spatialparams
detached
Status Name Job ID Coverage
  Trigger
manual full-dune-latest-release-clang
failed full-dune-latest-release-gcc

manual full-dune-master-gcc
manual minimal-dune-latest-release-gcc
 
  Downstream Modules
created trigger lecture