dev-cpp/cpp-taskflow: add missing doctest test dependency; fix double KEYWORDS

Closes: https://bugs.gentoo.org/826894
Signed-off-by: Sam James <sam@gentoo.org>

dev-cpp/cpp-taskflow/cpp-taskflow-9999.ebuild

@@ -10,7 +10,6 @@ HOMEPAGE="https://cpp-taskflow.github.io"
 if [[ ${PV} == 9999 ]]; then
 	EGIT_REPO_URI="https://github.com/cpp-taskflow/${PN}.git"
 	inherit git-r3
-	KEYWORDS=""
 	S="${WORKDIR}/cpp-taskflow-${PV}"
 else
 	SRC_URI="https://github.com/${PN}/${PN}/archive/v${PV}.tar.gz -> ${P}.tar.gz"
@@ -23,6 +22,8 @@ SLOT="0"
 IUSE="examples test"
 RESTRICT="!test? ( test )"
 
+DEPEND="test? ( dev-cpp/doctest )"
+
 HTML_DOCS=( docs/. )
 
 src_prepare() {