The `signature` directive added by commit 74e3c1d313 (Utilities/Sphinx:
Add a directive to document command signatures, 2023-02-24) will be
commonly used with the form:
.. signature::
some_command(SOME_SIGNATURE)
Docs for this signature.
Drop the assumption that all CMake domain directives are immediately
followed by their argument on the same line.
8c52458a9e