xrefautomaticsectiontitle appears to be available from texinfo 5.0 or
greater. As such, it is not worthwhile to add requirement for a minimum
necessary makeinfo version. So remove the usage of it.
Also align node name with section title where possible.
ChangeLog:
* libsframe/doc/sframe-spec.texi: Remove usage of
xrefautomaticsectiontitle.
cbff1430f8