Add alt-text for ml-ops-cycle fig on main page

[batpigandme]

The ML-Ops Cycle figure currently has no alt text.

Full description of issue generated by axe here: https://axe.deque.com/issues/aa5f97db-69dd-4ed6-9629-a3d70d7e94c8

Relevant line in the docs is here: https://github.com/juliasilge/vetiver.dev/blob/4424dadcf46e5a1cf9bf40784ebe4dc6b31c3381/index.qmd#L14

Solution: Add a space in after fig-align="center" in the curly braces followed by fig-alt="Whatever the alt text should be."

[juliasilge]

Closed in 546630b8ae7545d80e708f93f58f9d956fed3e18