Remove real-overseer 🎉 (#2834)

* remove real-overseer

* overseer: only activate leaves which support parachains

* integrate HeadSupportsParachains into service

* remove unneeded line

polkadot/scripts/gitlab/test_linux_stable.sh

@@ -4,7 +4,4 @@ set -e
 #shellcheck source=../common/lib.sh
 source "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/../common/lib.sh"
 
-time cargo test --all --release --verbose --locked --features=runtime-benchmarks --features=real-overseer
-
-cd parachain/test-parachains/adder/collator/
-time cargo test --release --verbose --locked --features=real-overseer
+time cargo test --all --release --verbose --locked --features=runtime-benchmarks