Remove bugfix for positioning icon in multi-line admonitions

[stevepiercy]

In #49, I applied a bugfix for correctly positioning multi-line admonitions.

The upstream theme PyData Sphinx Theme merged my bugfix in pydata/pydata-sphinx-theme#2100 for pydata/pydata-sphinx-theme#2099. It has not yet been released.

When it is released, then we should remove this fix to avoid conflicts.