Revert "allow unstable sys-libs/libstatgrab"

This reverts commit bdb1dc114a.

(Unstable) app-admin/collectd doesn't compile with unstable
sys-libs/libstatgrab...

weekly/sys-libs.particle

@@ -11,7 +11,6 @@ packages:
 	sys-libs/libraw1394,
 	sys-libs/libsafe,
 	sys-libs/libsmbios,
-	sys-libs/libstatgrab,
 	sys-libs/openipmi,
 	sys-libs/pwdb,
 	sys-libs/talloc,

weekly/sys-libs.stable.particle

@@ -22,6 +22,7 @@ packages:
 	sys-libs/libosinfo,
 	sys-libs/libseccomp,
 	sys-libs/libsepol,
+	sys-libs/libstatgrab,
 	sys-libs/libstdc++-v3,
 	sys-libs/libtermcap-compat,
 	sys-libs/libtrash,