Documentation added by

* commit 4f4f2028 (Help: Add documentation for buildPresets and
                     testPresets, 2021-01-13, v3.20.0-rc1~51^2~7)
* commit 676ecf0d (cmake-presets: Add build and test presets,
                     2020-12-14, v3.20.0-rc1~51^2~6)

used square brackets in the `cmake --build` signature to indicate
non-optional alternatives, which is not a typical convention.
A common convention is to use parentheses instead, but in this
case it is probably clearer to list the two signatures separately.

Fixes: #22413