texinfo: don't create dependency on INHERIT variable

texinfo: don't create dependency on INHERIT variable

* we don't want the do_package signature depending on INHERIT variable
* e.g. just adding the own-mirrors causes texinfo to rebuild:
  # bitbake-diffsigs BUILD/sstate-diff/*/*/texinfo/*do_package.sig*
  basehash changed from 015df2fd8e396cc1e15622dbac843301 to 9f1d06c4f238c70a99ccb6d8da348b6a
  Variable INHERIT value changed from
  ' rm_work blacklist blacklist report-error ${PACKAGE_CLASSES} ${USER_CLASSES} ${INHERIT_DISTRO} ${INHERIT_BLACKLIST} sanity'
  to
  ' rm_work own-mirrors blacklist blacklist report-error ${PACKAGE_CLASSES} ${USER_CLASSES} ${INHERIT_DISTRO} ${INHERIT_BLACKLIST} sanity'

(From OE-Core rev: ac6642e9a84a67c8cdaa8d8e939c2d0e2dcb3577)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>