Clean up the GitHub Pages documentation

[ktbolt]

Use Case

We need to remove redundant documentation from GitHub Pages.

Problem

Most of the GitHub Pages documentation has been moved to https://simvascular.github.io/documentation/rom_simulation.html#0d-solver.

Solution

Remove redundant documentation from GitHub Pages.

Alternatives considered

None.

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

[menon-karthik]

I will do this in the next couple of days.

[ktbolt]

Not quite there, I will tidy up a bit.