Change Acknowledgments header to a level 2 header

Author: Karol-G

README.md

@@ -81,7 +81,7 @@ If you encounter any problems, please file an issue along with a detailed descri
 [pip]: https://pypi.org/project/pip/
 [PyPI]: https://pypi.org/
 
-# Acknowledgments
+## Acknowledgments
 
 <p align="left">
   <img src="https://github.com/MIC-DKFZ/vidata/raw/main/imgs/Logos/HI_Logo.png" width="150"> &nbsp;&nbsp;&nbsp;&nbsp;