devel/py-Automat: update to 25.4.16

Port changes:

• Update to 25.4.16
• Update BUILD_DEPENDS devel/py-setuptools_scm7 -> devel/py-setuptools-scm

Upstream changes:

• https://github.com/glyph/automat/releases/tag/v25.4.16

PR: 287674
Reported by: John W. O'Brien <john@saltant.com> (maintainer)