refactor: optional support for legacy dependencies keyword

include/jvalidate/constraint.h

@@ -57,8 +57,7 @@ private:
       {"anyOf", {{schema::Version::Draft04, &Self::anyOf}}},
       {"const", {{schema::Version::Draft06, &Self::isConstant}}},
       {"contains", {{schema::Version::Draft06, &Self::contains}}},
-      {"dependencies",
-       {{schema::Version::Draft04, &Self::dependencies}, {schema::Version::Draft2019_09, nullptr}}},
+      {"dependencies", {{schema::Version::Draft04, &Self::dependencies}}},
       {"dependentRequired", {{schema::Version::Draft2019_09, &Self::dependentRequired}}},
       {"dependentSchemas", {{schema::Version::Draft2019_09, &Self::dependentSchemas}}},
       {"divisibleBy",