CompatHelper: bump compat for MCMCChains to 6 for package test, (keep existing compat)

Author: CompatHelper Julia

test/Project.toml

@@ -29,7 +29,7 @@ DistributionsAD = "0.6.3"
 Documenter = "0.26.1, 0.27"
 ForwardDiff = "0.10.12"
 LogDensityProblems = "2"
-MCMCChains = "4.0.4, 5"
+MCMCChains = "4.0.4, 5, 6"
 MacroTools = "0.5.5"
 Setfield = "0.7.1, 0.8, 1"
 StableRNGs = "1"