Fix CI check and remove try-runtime command (#3046)

* CI: Fix check-try-runtime

(preparation for the monorepo)

Warnings should be treated as errors here, since this is how it will
be done in the monorepo.
I expect to see two errors in this check now.

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Allow deprecated

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Remove try-runtime command

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* make it compile

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Remove try-runtime-cli dependency

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

cumulus/scripts/ci/gitlab/pipeline/test.yml

@@ -65,6 +65,8 @@ cargo-check-try-runtime:
   extends:
     - .docker-env
     - .common-refs
+  variables:
+    RUSTFLAGS: "-D warnings"
   # this is an artificial job dependency, for pipeline optimization using GitLab's DAGs
   needs:
     - job: check-runtime-benchmarks