bump julia compat to 1.6^

Author: ablaom

Project.toml

@@ -11,7 +11,7 @@ Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 [compat]
 DecisionTree = "0.10"
 MLJModelInterface = "^0.3,^0.4, 1.0"
-julia = "1"
+julia = "1.6"
 
 [extras]
 CategoricalArrays = "324d7699-5711-5eae-9e2f-1d82baa6b597"