bin/bashrc-functions.sh: remove portageq function

Since commit 0cc4c1ac21a2ea94cfb1f6ff4b461a9e349d47df,
$PORTAGE_BIN_PATH/portageq no longer exists, which breaks the portageq
shell function inside bashrc-functions.sh. Note that
$PORTAGE_BIN_PATH/ebuild-helpers/portageq is in $PATH, so we can simply
remove the redundant function.

Fixes: 0cc4c1a ("Install Portage using setup.py")
X-Gentoo-Bug: 524964
X-Gentoo-URL: https://bugs.gentoo.org/show_bug.cgi?id=524964
Acked-by: Alexander Berntsen <bernalex@gentoo.org>