v0.5.6

ProbNumDiffEq v0.5.6

Diff since v0.5.5

Merged pull requests:

• Check that nf is correct for SecondOrderODEProblems (#109) (@nathanaelbosch)
• Fix the documentation github action (#112) (@nathanaelbosch)
• Remove the prior field from the ODE filter algorithms (#113) (@nathanaelbosch)