chore(docdb): non-TS examples fail to build due to the wrong enum being used (#20906)

Due to a bug in jsii, only the first instance of enums that have duplicate values appear in non-TS languages. This means that non-TS examples that use the enums that do not appear fail to build. This PR changes the enums used to fix the failing examples.

fixes #20747

----

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### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/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/main/INTEGRATION_TESTS.md)?
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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*

Author: josephedward

packages/@aws-cdk/aws-docdb/README.md

@@ -25,7 +25,7 @@ const cluster = new docdb.DatabaseCluster(this, 'Database', {
     excludeCharacters: '\"@/:', // optional, defaults to the set "\"@/" and is also used for eventually created rotations
     secretName: '/myapp/mydocdb/masteruser', // optional, if you prefer to specify the secret name
   },
-  instanceType: ec2.InstanceType.of(ec2.InstanceClass.R5, ec2.InstanceSize.LARGE),
+  instanceType: ec2.InstanceType.of(ec2.InstanceClass.MEMORY5, ec2.InstanceSize.LARGE),
   vpcSubnets: {
     subnetType: ec2.SubnetType.PUBLIC,
   },
@@ -78,7 +78,7 @@ const cluster = new docdb.DatabaseCluster(this, 'Database', {
   masterUser: {
     username: 'myuser',
   },
-  instanceType: ec2.InstanceType.of(ec2.InstanceClass.R5, ec2.InstanceSize.LARGE),
+  instanceType: ec2.InstanceType.of(ec2.InstanceClass.MEMORY5, ec2.InstanceSize.LARGE),
   vpcSubnets: {
     subnetType: ec2.SubnetType.PUBLIC,
   },
@@ -150,7 +150,7 @@ const cluster = new docdb.DatabaseCluster(this, 'Database', {
   masterUser: {
     username: 'myuser',
   },
-  instanceType: ec2.InstanceType.of(ec2.InstanceClass.R5, ec2.InstanceSize.LARGE),
+  instanceType: ec2.InstanceType.of(ec2.InstanceClass.MEMORY5, ec2.InstanceSize.LARGE),
   vpcSubnets: {
     subnetType: ec2.SubnetType.PUBLIC,
   },