change flatten to Array#flat (Node 10.x EOL)

index.js

@@ -2,8 +2,6 @@
 
 // TODO: Rename this to something more appropriate, like any/anyOf? How to make sure that doesn't cause confusion with `oneOf`?
 
-const flatten = require("flatten");
-
 const ValidationError = require("@validatem/error");
 const combinator = require("@validatem/combinator");
 const validationResult = require("@validatem/validation-result");
@@ -14,13 +12,13 @@ const areErrorsFromSameOrigin = require("./src/are-errors-from-same-origin");
 function unpackNestedEithers(errors) {
 	// NOTE: We only unpack `either` errors that occurred *at the same level* as this error, ie. where there's directly a case of `either(either(...), ...)`, without any kind of data nesting (like `arrayOf` or `hasShape`) inbetween. Nested-data failures should still be shown separately, as their resolution strategy is actually different; unlike same-level nested `either` errors, where the nesting is purely an implementation detail that allows composing sets of alternatives together.
 
-	return flatten(errors.map((error) => {
+	return (errors.map((error) => {
 		if (error.path.length === 0 && error.__isValidatemEitherError) {
 			return error.subErrors;
 		} else {
 			return error;
 		}
-	}));
+	})).flat();
 }
 
 function hasNestedPaths(error) {

package.json

@@ -20,7 +20,6 @@
     "@validatem/combinator": "^0.1.1",
     "@validatem/error": "^1.0.0",
     "@validatem/match-validation-error": "^0.1.0",
-    "@validatem/validation-result": "^0.1.2",
+    "@validatem/validation-result": "^0.1.2"
-    "flatten": "^1.0.3"
   }
 }