change the chainrulestestutils compat bound

Author: Miha Zgubic

Project.toml

@@ -13,7 +13,7 @@ Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 
 [compat]
 ChainRulesCore = "0.9.29"
-ChainRulesTestUtils = "0.6.1"
+ChainRulesTestUtils = "0.6.6"
 Compat = "3"
 FiniteDifferences = "0.11, 0.12"
 Reexport = "0.2, 1"