Reorganize clickable title and ecosystem link

[kevinsung]

Example from https://qiskit-extensions.github.io/qiskit-experiments/:

Clicking on "Qiskit Ecosystem" brings the user to the Qiskit ecosystem home page (probably not what the user wants). However, clicking on "Qiskit Experiments" doesn't bring you to the Qiskit Experiments documentation page (probably what the user wants).

[kevinsung]

At the ecosystem meeting we decided:

• The clickable title should be the name of the package, like in the default Furo theme.
• Remove the Qiskit ecosystem logo. Instead, put the following text below the title, in smaller font:

This project is part of the Qiskit ecosystem.

[Eric-Arellano]

This is modified in https://github.com/Qiskit/qiskit_sphinx_theme/blob/main/src/qiskit_sphinx_theme/theme/qiskit-sphinx-theme/custom_templates/sidebar_brand.html.