Unnecessary fence in quadrature operator

[EmilyBourne]

A seemingly unnecessary fence was added in the quadrature operator in !586. This allows the code to avoid a seg fault which appears when compiling certain CPU functions using CPU quadrature with a compilation configured with KOKKOS_SERIAL=ON and KOKKOS_CUDA=ON. The seg fault only appears when compiling in Release mode.

A issue will be opened in DDC with a reproducer. When the issue has been investigated (and hopefully fixed) the fence should be removed.