Update GraphQL Playground to v1.7.32. (#3702)

* Update GraphQL Playground to v1.7.32.

This fixes a small, rogue, often invisible curly brace that was appearing on
the top-right side of GraphQL Playground's interface.  See referenced issue
for details.

Ref: apollographql/graphql-playground#21
Cc: @tizmagik

* Add CHANGELOG.md for #3702.

CHANGELOG.md

@@ -9,7 +9,7 @@ The version headers in this history reflect the versions of Apollo Server itself
 
 > The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  When a release is being prepared, a new header will be (manually) created below and the the appropriate changes within that release will be moved into the new section.
 
-- _Nothing yet! Stay tuned._
+- `apollo-server-core`: Update GraphQL Playground to latest version to remove a rogue curly-brace appearing in the top-right corner of the interface under certain conditions. [PR #3702](https://github.com/apollographql/apollo-server/pull/3702) [Playground PR](https://github.com/apollographql/graphql-playground/pull/21)
 
 ### v2.10.0
 

packages/apollo-server-core/src/playground.ts

@@ -10,7 +10,7 @@ export {
 // This specifies the version of `graphql-playground-react` that will be served
 // from `graphql-playground-html`.  It's passed to ``graphql-playground-html`'s
 // renderPlaygroundPage` via the integration packages' playground configuration.
-const playgroundVersion = '1.7.31';
+const playgroundVersion = '1.7.32';
 
 // https://stackoverflow.com/a/51365037
 type RecursivePartial<T> = {