sys-devel/bison: Sync with Gentoo

It's from Gentoo commit 78213a89b4a602460bf81ba5fab8eed561091ade.

Author: Flatcar Buildbot

sdk_container/src/third_party/portage-stable/sys-devel/bison/bison-3.8.2-r2.ebuild

@@ -3,7 +3,7 @@
 
 EAPI=8
 
-VERIFY_SIG_OPENPGP_KEY_PATH="${BROOT}"/usr/share/openpgp-keys/bison.asc
+VERIFY_SIG_OPENPGP_KEY_PATH=/usr/share/openpgp-keys/bison.asc
 inherit flag-o-matic verify-sig
 
 DESCRIPTION="A general-purpose (yacc-compatible) parser generator"