fix exportKind declaration in babel-types (#10126)

* fix exportKind types declaration for ExportNamedDeclaration and DeclareExportAllDeclaration in babel-types

* revert `let` in exportKind in babel-parser types

packages/babel-types/src/definitions/es2015.js

@@ -5,6 +5,7 @@ import defineType, {
   chain,
   assertEach,
   assertOneOf,
+  validateOptional,
 } from "./utils";
 import {
   functionCommon,
@@ -260,6 +261,7 @@ defineType("ExportNamedDeclaration", {
       validate: assertNodeType("StringLiteral"),
       optional: true,
     },
+    exportKind: validateOptional(assertOneOf("type", "value")),
   },
 });
 

packages/babel-types/src/definitions/flow.js

@@ -150,7 +150,7 @@ defineType("DeclareExportAllDeclaration", {
   aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
   fields: {
     source: validateType("StringLiteral"),
-    exportKind: validateOptional(assertOneOf(["type", "value"])),
+    exportKind: validateOptional(assertOneOf("type", "value")),
   },
 });