Fix qgsfunction docs formatting

[DelazJ]

as displayed at https://qgis.org/pyqgis/master/core/qgsfunction.html#qgis.core.qgsfunction

Something I don't understand is that the code lists as keyword arguments the last three but the API docs shows all of them under the keyword arguments list.

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit 0ed433c)

🍎 MacOS Qt6 builds

Download MacOS Qt6 builds of this PR for testing.
This installer is not signed, control+click > open the app to avoid the warning
(Built from commit 0ed433c)

[nyalldawson]

Superseded by #62634

@DelazJ

Something I don't understand is that the code lists as keyword arguments the last three but the API docs shows all of them under the keyword arguments list.

It's confusing, but the actual method shown in the docs is the decorator -- https://github.com/qgis/QGIS/blob/master/python/core/additions/qgsfunction.py#L178