Prevent rendering nested content elements created by `content_blocks` extension

# Bug Report

## Prerequisites

* [ ] Can you reproduce the problem on TYPO3 v11.5 LTS
* [x] Can you reproduce the problem on TYPO3 v12.4 LTS
* [x] Did you [perform a cursory search](https://github.com/issues?q=is%3Aissue+user%3Abenjaminkott+repo%3Abenjaminkott%2Fbootstrap_package)
to see if your bug or enhancement is already reported?

## Description

When creating nested content element with content blocks the content rendered twice on same page.
The `lib.dynamicContent ` schould be modified to prevent such case.

Possible solution:

```typoscript
# Prevent rendering nested content elements created by `content_blocks` extension
[extension.isLoaded('content_blocks') == 1]
lib.dynamicContent.20.select.where {
postUserFunc = TYPO3\CMS\ContentBlocks\UserFunction\ContentWhere->extend
}
[end]
```

I can provide a PR if needed.

## Steps to Reproduce

1. Create a simple nested content element with content blocks:

```yaml
name: example/tabs
fields:
- identifier: header
useExistingField: true
- identifier: tabs_item
type: Collection
minitems: 1
foreign_table: tt_content
```

```html

```

### Expected behavior
Content should be only rendered once.

### Actual behavior

Content rendered twice.

### Screenshots


## Versions

TYPO3 v12.4.27
Content Blocks v0.7.19
PHP v8.2

Start by locating the lib.dynamicContent TypoScript configuration and reproduce the nested content-block case described in the issue with TYPO3 v12.4. Check how the Content Blocks extension contributes nested tt_content records to the selection. Done means the nested content is rendered only once without affecting ordinary dynamic content rendering.

Written by the indexing model from the issue text.