rds: CfnDBProxy is not taggable

### Describe the bug

rds.CfnDBProxy.tags is currently type `TagFormatProperty[]` which would not be considered as taggable based on [this logic](https://github.com/aws/aws-cdk/blob/ee85afb1429c2859bab3f0f6310dfbf37d323210/packages/aws-cdk-lib/core/lib/tag-aspect.ts#L74-L80).

I guess this is incorrectly typed.

### Expected Behavior

CfnDBProxy should be a taggable resource with correct type.

### Current Behavior

CfnDBProxy can't be tagged.

### Reproduction Steps

`Tags.of(proxy).add('foo','bar');`

and the L1 proxy resource will not be tagged.

### Possible Solution

correct the type of the CfnDBProxy resource.

### Additional Information/Context

_No response_

### CDK CLI Version

2.110.0

### Framework Version

_No response_

### Node.js Version

v18.16.0

### OS

mac os x

### Language

TypeScript

### Language Version

_No response_

### Other information

_No response_

Start with the taggability logic in packages/aws-cdk-lib/core/lib/tag-aspect.ts, then locate the CfnDBProxy tags declaration and compare its type with what that logic accepts. Reproduce the issue with Tags.of(proxy).add('foo','bar'); and confirm that CfnDBProxy is recognized as taggable with the corrected type.

Written by the indexing model from the issue text.