fix(sample-app): exclude all __pycache__ in cdk.json (#27191)

Following the cdk workshop for python I noticed that `cdk watch` watches files from `__pycache__`.

This is an attempt to fix that.

Steps to reproduce:
1. `cdk init sample-app --language python`
2. `cdk bootstrap`
3. Run `cdk watch` and  notice that `__pycache__` folders are being watched:
```
'watch' is observing directory 'cdk_workshop/__pycache__' for changes
'watch' is observing the file 'cdk_workshop/cdk_workshop_stack.py' for changes
'watch' is observing the file 'cdk_workshop/__pycache__/__init__.cpython-311.pyc' for changes
'watch' is observing the file 'cdk_workshop/__pycache__/cdk_workshop_stack.cpython-311.pyc' for changes
```

----

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

packages/aws-cdk/lib/init-templates/app/python/cdk.template.json

@@ -8,7 +8,7 @@
  "requirements*.txt",
  "source.bat",
  "**/__init__.py",
- "python/__pycache__",
+ "**/__pycache__",
  "tests"
  ]
  }