Remove std feature from CI workflow

Signed-off-by: Tin Svagelj <tin.svagelj@live.com>

.github/workflows/rust.yml

@@ -19,6 +19,6 @@ jobs:
       - name: Build no_std all features
         run: cargo build --verbose --no-default-features --features no_std,debug,ptr_metadata,error_in_core
       - name: Build all features
-        run: cargo build --verbose --no-default-features --features std,debug,ptr_metadata,error_in_core
+        run: cargo build --verbose --no-default-features --features debug,ptr_metadata,error_in_core
       - name: Run tests
         run: cargo test --verbose --features ptr_metadata