Sign 1.6.0~rc1 testing

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

1.6.0~rc1/sysupgrade/testing.manifest

@@ -290,3 +290,4 @@ x86-legacy 1.6.0~rc1 ece54579aed9e817e0f3e1cef814d6e61886d8a7de3d649bd6f10759b3e
 x86-64 1.6.0~rc1 a5da9e1c8c16b6dfbb588a84b3505cd4b855b811638879a080633cab757a287b 13589297 gluon-ffho-1.6.0~rc1-x86-64-sysupgrade.img.gz
 ---
 dea4e5668704216083c915d363eab4403a54293805f5dba5310f377c0e3e9b095e8255c1dc1ec88d19899fe24f092bccd2319e1e732cf16a5c0280674e4f550a
+a993c1a112f5ebd90eba9dc8fd9f9a9e5a9a8dbe2e8348640290798b98ef2a03ff469d010cf6daa186fd7e4b19ca44b93529a2d02aa0974f98bc61182b183302