Inline PrintSchemaOptions type, whose parent module has been moved.

This option will likely be deprecated in `graphql@16`.  For now, we'll
inline this type into this module to continue emitting it into the
declaration file for `makeRemoteExecutableSchema`.

This is necessary since the TypeScript compiler can no longer resolve its
previous location as `graphql` has moved the location of the `schemaPrinter`
module to `printSchema` in graphql/graphql-js#2426.

cc @IvanGoncharov

src/stitching/makeRemoteExecutableSchema.ts

@@ -31,7 +31,6 @@ import resolveParentFromTypename from './resolveFromParentTypename';
 import defaultMergedResolver from './defaultMergedResolver';
 import { checkResultAndHandleErrors } from './errors';
 import { observableToAsyncIterable } from './observableToAsyncIterable';
-import { Options as PrintSchemaOptions } from 'graphql/utilities/schemaPrinter';
 
 export type ResolverFn = (
   rootValue?: any,
@@ -49,6 +48,27 @@ export type FetcherOperation = {
   context?: { [key: string]: any };
 };
 
+/**
+ * This type has been copied inline from its source on `@types/graphql`:
+ *
+ * https://git.io/Jv8NX
+ *
+ * Previously, it was imported from `graphql/utilities/schemaPrinter`, however
+ * that module has been removed in `graphql@15`.  Furthermore, the sole property
+ * on this type is due to be deprecated in `graphql@16`.
+ */
+interface PrintSchemaOptions {
+  /**
+   * Descriptions are defined as preceding string literals, however an older
+   * experimental version of the SDL supported preceding comments as
+   * descriptions. Set to true to enable this deprecated behavior.
+   * This option is provided to ease adoption and will be removed in v16.
+   *
+   * Default: false
+   */
+  commentDescriptions?: boolean;
+}
+
 export default function makeRemoteExecutableSchema({
   schema,
   link,