bump cargo dependencies (#545)

- Update PVM to fix a downstream bug.
- Update the polkadot-sdk to get rid of most retester exceptions.

Signed-off-by: xermicus <cyrill@parity.io>

.github/workflows/differential-tests.yml

@@ -138,9 +138,9 @@ jobs:
     env:
       # Commit SHA that produced the polkadot-sdk crate pinned in Cargo.toml,
       # obtained from the crate's .cargo_vcs_info.json via:
-      # curl -sL https://crates.io/api/v1/crates/polkadot-sdk/<VERSION>/download | tar xzO '*/.cargo_vcs_info.json'
-      # Current version: 2603.0.0
-      POLKADOT_SDK_REF: "c56b086a3cfcb3a48b75fd1ef9c77ad9b7408b95"
+      # curl -sL -A "user-agent" https://crates.io/api/v1/crates/polkadot-sdk/<VERSION>/download | tar xzO polkadot-sdk-<VERSION>/.cargo_vcs_info.json
+      # Current version: 2604.2.0
+      POLKADOT_SDK_REF: "54095b130013902aaaa33a69dbbf980144764afb"
       RUSTFLAGS: "-Awarnings"
     steps:
       - name: Checkout revive
@@ -186,7 +186,7 @@ jobs:
       - name: Set Up Rust Toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: "1.90.0"
+          toolchain: "1.91.0"
           target: "wasm32-unknown-unknown"
           components: "rust-src"
           rustflags: ""