Updated badges in the readme file

Author: sebprt

README.md

@@ -5,7 +5,7 @@ This package brings tools to read and write into spreadsheet files from a pipeli
 
 
 [![Quality](https://github.com/php-etl/spreadsheet-flow/actions/workflows/quality.yaml/badge.svg)](https://github.com/php-etl/spreadsheet-flow/actions/workflows/quality.yaml)
-[![PHPStan level 5](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-5.yaml/badge.svg)](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-5.yaml)
+[![PHPStan level 6](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-6.yaml/badge.svg)](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-6.yaml)
 [![PHPStan level 7](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-7.yaml/badge.svg)](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-7.yaml)
 [![PHPStan level 8](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-8.yaml/badge.svg)](https://github.com/php-etl/spreadsheet-flow/actions/workflows/phpstan-8.yaml)
 ![PHP](https://img.shields.io/packagist/php-v/php-etl/spreadsheet-flow)