[AWS::Lambda::Function] - [BUG] - False-positive drift for `Code/SourceKMSKeyArn`

### Name of the resource

AWS::Lambda::Function

### Resource Name

_No response_

### Issue Description

We found a false-positive CloudFormation drift for

```yaml
Lambda:
Type: AWS::Lambda::Function
Properties:
Role: !GetAtt LambdaRole.Arn
Handler: index.lambda_handler
Runtime: python3.13
Timeout: 120
LoggingConfig:
LogGroup: !Ref LambdaLogGroup
MemorySize: 128
Architectures:
- arm64
Code:
SourceKMSKeyArn: !GetAtt KMSKey.Arn # <--------------------------
ZipFile: |
def lambda_handler(event, context):

print("Test")
```

Property | Change | Expected value | Current value
-- | -- | -- | --
Code | REMOVE | {"SourceKMSKeyArn":"arn:aws:kms:..."} | -

### Expected Behavior

CloudFormation Drift Detection is able to find the configuration.

### Observed Behavior

It doesn't work.

### Test Cases

```yaml
AWSTemplateFormatVersion: 2010-09-09
Description: Test

Resources:
KMSKey:
Type: AWS::KMS::Key
Properties:
KeyPolicy:
Version: 2012-10-17
Id: !Sub "${AWS::AccountId}-${AWS::StackName}"
Statement:
- Sid: "Allow root"
Effect: Allow
Action: kms:*
Resource: "*"
Principal:
AWS: !Sub "arn:aws:iam::${AWS::AccountId}:root"
- Sid: "Lambda: Allow Lambda to access KMS Key."
Effect: Allow
Principal:
Service: lambda.amazonaws.com
Action:
- kms:GenerateDataKey
- kms:Decrypt
Resource: "*"
Condition:
StringLike:
kms:EncryptionContext:aws:lambda:FunctionArn: !Sub "arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:*"

LambdaRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Statement:
- Effect: Allow
Principal:
Service: lambda.amazonaws.com
Action: sts:AssumeRole
Policies:
- PolicyName: "InlinePolicy"
PolicyDocument:
Version: 2012-10-17
Statement:
- Sid: "LogAccess"
Effect: Allow
Action:
- logs:CreateLogStream
- logs:PutLogEvents
Resource: !GetAtt LambdaLogGroup.Arn

Lambda:
Type: AWS::Lambda::Function
Properties:
Role: !GetAtt LambdaRole.Arn
Handler: index.lambda_handler
Runtime: python3.13
Timeout: 120
LoggingConfig:
LogGroup: !Ref LambdaLogGroup
MemorySize: 128
Architectures:
- arm64
Code:
SourceKMSKeyArn: !GetAtt KMSKey.Arn
ZipFile: |
def lambda_handler(event, context):

print("Test")

LambdaLogGroup:
Type: AWS::Logs::LogGroup
Properties:
LogGroupName: !Sub "/${AWS::StackName}/Lambda"
RetentionInDays: 30
```

### Other Details

_No response_

The issue names no repository files or tests. Start by deploying the provided CloudFormation template and running drift detection on the Lambda resource; done means Code.SourceKMSKeyArn is detected instead of being reported as removed.

Written by the indexing model from the issue text.