dev-python/pypy3-exe: Remove dead USE=sandbox

Closes: https://bugs.gentoo.org/704376
Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/pypy3-exe/metadata.xml

@@ -9,7 +9,6 @@
 		<flag name="low-memory">Build using PyPy with the engine configured towards low memory footprint.
 			This makes it possible to build PyPy using ~3.5G of RAM on amd64 and ~half of that on x86,
 			at the cost of lengthened build time.</flag>
-		<flag name="sandbox">Enable sandboxing functionality</flag>
 	</use>
 	<upstream>
 		<remote-id type="bitbucket">pypy/pypy</remote-id>

dev-python/pypy3-exe/pypy3-exe-7.3.0.ebuild

@@ -16,7 +16,7 @@ S="${WORKDIR}/${MY_P}-src"
 LICENSE="MIT"
 SLOT="${PV}"
 KEYWORDS="~amd64 ~ppc64 ~x86 ~amd64-linux ~x86-linux"
-IUSE="bzip2 +jit low-memory ncurses sandbox cpu_flags_x86_sse2"
+IUSE="bzip2 +jit low-memory ncurses cpu_flags_x86_sse2"
 
 RDEPEND=">=sys-libs/zlib-1.1.3:0=
 	virtual/libffi:0=
@@ -98,7 +98,6 @@ src_configure() {
 	local args=(
 		--no-shared
 		$(usex jit -Ojit -O2)
-		$(usex sandbox --sandbox '')
 
 		${jit_backend}