CompatHelper: bump compat for MCMCChains to 6 for package test, (keep existing compat) (#467)

This pull request changes the compat entry for the `MCMCChains` package from `4.0.4, 5` to `4.0.4, 5, 6` for package test.
This keeps the compat entries for earlier versions.



Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

Co-authored-by: Hong Ge <[email protected]>

Author: github-actions[bot]

test/Project.toml

@@ -22,14 +22,14 @@ Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [compat]
 AbstractMCMC = "2.1, 3.0, 4"
-AbstractPPL = "0.5.1, 0.6"
+AbstractPPL = "0.5"
 Bijectors = "0.11, 0.12"
 Distributions = "0.25"
 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"