Revert "sys-libs/readline: Mark 8.0 stable."

This reverts commit a3969b80816bd5fe601be3f18b8e211e8d8ab10b.

Reason for revert: Breaks chroot.

Exempt-From-Owner-Approval: Cherry-pick into a stabilize branch.

Original change's description:
> sys-libs/readline: Mark 8.0 stable.
>
> BUG=chromium:1117585
> TEST=CQ passes
>
> Change-Id: Ic2dc006fee419376a27f4c05ee26e9da216e2353
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2500466
> Reviewed-by: Allen Webb <allenwebb@google.com>
> Commit-Queue: Navil Perez <navil@google.com>
> Tested-by: Navil Perez <navil@google.com>

Bug: chromium:1141644
Change-Id: I85480187b9587accb128e3dcb373037993439d46
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2508257
Tested-by: Navil Perez <navil@google.com>
Commit-Queue: Navil Perez <navil@google.com>
Reviewed-by: Navil Perez <navil@google.com>
diff --git a/sys-libs/readline/readline-8.0_p4.ebuild b/sys-libs/readline/readline-8.0_p4.ebuild
index 2978d11..530bd1c 100644
--- a/sys-libs/readline/readline-8.0_p4.ebuild
+++ b/sys-libs/readline/readline-8.0_p4.ebuild
@@ -41,7 +41,7 @@
 
 LICENSE="GPL-3"
 SLOT="0/8"  # subslot matches SONAME major
-KEYWORDS="*"
+KEYWORDS="~*"
 IUSE="static-libs +unicode utils"
 
 RDEPEND=">=sys-libs/ncurses-5.9-r3:0=[static-libs?,unicode?,${MULTILIB_USEDEP}]"