chore(aws-auth): fix a typo in a comment (#19779)

Fix a typo in a comment.
----

### All Submissions:

* [x] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [ ] Did you use `cdk-integ` to deploy the infrastructure and generate the snapshot (i.e. `cdk-integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: joe-king-sh

packages/aws-cdk/lib/api/aws-auth/account-cache.ts

@@ -61,7 +61,7 @@ export class AccountAccessKeyCache {
     return map[accessKeyId];
   }
 
-  /** Put a mapping betweenn access key and account ID */
+  /** Put a mapping between access key and account ID */
   public async put(accessKeyId: string, account: Account) {
     let map = await this.loadMap();