docs(kinesis): correct grantRead and grantWrite comments (#14707)

This commit swaps the comments for `grantRead` and `grantWrite` so that the comments match the permissions being granted. 

No extra verification was done for this change, as it only effects comments. 

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

packages/@aws-cdk/aws-kinesis/lib/stream.ts

@@ -326,7 +326,7 @@ abstract class StreamBase extends Resource implements IStream {
   public abstract readonly encryptionKey?: kms.IKey;
 
   /**
-   * Grant write permissions for this stream and its contents to an IAM
+   * Grant read permissions for this stream and its contents to an IAM
    * principal (Role/Group/User).
    *
    * If an encryption key is used, permission to ues the key to decrypt the
@@ -343,10 +343,10 @@ abstract class StreamBase extends Resource implements IStream {
   }
 
   /**
-   * Grant read permissions for this stream and its contents to an IAM
+   * Grant write permissions for this stream and its contents to an IAM
    * principal (Role/Group/User).
    *
-   * If an encryption key is used, permission to ues the key to decrypt the
+   * If an encryption key is used, permission to ues the key to encrypt the
    * contents of the stream will also be granted.
    */
   public grantWrite(grantee: iam.IGrantable) {