chore(lambda): fix addPermission function name in docs (aws#18991)

Documentation text change based on open issue aws#17873 indicating there is a typo.

fixes aws#17873 

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packages/@aws-cdk/aws-lambda/lib/permission.ts

@@ -3,7 +3,7 @@ import { Construct } from '@aws-cdk/core';
 
 /**
  * Represents a permission statement that can be added to a Lambda function's
- * resource policy via the `addPermissions()` method.
+ * resource policy via the `addPermission()` method.
  */
 export interface Permission {
   /**