Updates for Doxygen 1.9.5

[chrisrichardson]

• Update Doxyfile
• Add some fixes for sphinx

[jorgensd]

I get some issues building the docs locally:

/root/shared/dolfinx/cpp/doc/source/fem.rst:64: WARNING: Parsing of expression failed. Using fallback parser. Error was:
Error in postfix expression, expected primary expression or type.
If primary expression:
  Invalid C++ declaration: Expected identifier in nested name. [error at 205]
    std::pair< DofMap, std::vector< std::int32_t > > collapse (MPI_Comm comm, const mesh::Topology &topology, const std::function< std::vector< int >(const graph::AdjacencyList< std::int32_t > &)> &reorder_fn=[](const graph::AdjacencyList< std::int32_t > &g) { return graph::reorder_gps(g);}) const
    -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------^
If type:
  Invalid C++ declaration: Expected identifier in nested name. [error at 205]
    std::pair< DofMap, std::vector< std::int32_t > > collapse (MPI_Comm comm, const mesh::Topology &topology, const std::function< std::vector< int >(const graph::AdjacencyList< std::int32_t > &)> &reorder_fn=[](const graph::AdjacencyList< std::int32_t > &g) { return graph::reorder_gps(g);}) const
    -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------^

related to https://github.com/FEniCS/dolfinx/blob/chris/doxygen/cpp/dolfinx/fem/DofMap.h#L144-L146
These issues only happen with the latest sphinx 5.3.0, not with 5.02 which we have pinned to on CI

[jorgensd]

Probably related to sphinx-doc/sphinx#10152

[jorgensd]

Looks good. See general comment regarding sphinx

[chrisrichardson]

I have the same warning with sphinx - but the docs still seem to build OK.