Remove unnecessary feature attributes

Author: dinowernli

.github/workflows/test.yaml

@@ -9,14 +9,14 @@ jobs:
       PROJECT_NAME_UNDERSCORE: concord
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
           toolchain: nightly
           override: true
       - name: Cargo cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry

src/main.rs

@@ -1,6 +1,3 @@
-#![feature(async_closure)]
-#![feature(trait_upcasting)]
-
 extern crate structopt;
 extern crate tracing;