devel/py-setuptools_scm: Adjust BUILD_DEPENDS

• Remove devel/py-wheel from BUILD_DEPENDS as it leads to circular dependencies under certain conditions, e.g. when the non-default option SIGNATURE of devel/py-wheel is enabled.
  
  Although devel/py-wheel is listed in "pyproject.toml", it is not needed during build, nor does it result in different package content.

PR: 261920
Reported by: Phil Pennock