docs: fix indentation and formatting in README

Closes #62488

Author: hightechandfood-lgtm

README.md

@@ -1,9 +1,9 @@
-<picture align="center">
+<picture>
   <source media="(prefers-color-scheme: dark)" srcset="https://pandas.pydata.org/static/img/pandas_white.svg">
   <img alt="Pandas Logo" src="https://pandas.pydata.org/static/img/pandas.svg">
 </picture>
 
------------------
+---
 
 # pandas: A Powerful Python Data Analysis Toolkit