remove old badge from readme

Author: fsbraun

README.rst

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  django CMS form builder
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-|pypi| |coverage| |python| |django| |djangocms| |djangocms4|
+|pypi| |coverage| |python| |django| |djangocms|
 
 **djangocms-form-builder** supports rendering of styled forms. The objective is to tightly integrate forms in the website design. **djangocms-form-builder** allows as many forms as you wish on one page. All forms are **xhr-based**. To this end, **djangocms-form-builder** extends the django CMS plugin model allowing a form plugin to receive xhr post requests.