chore: update CI minimum to 1.81.0

Author: XAMPPRocky

.github/workflows/rust.yml

@@ -19,7 +19,7 @@ jobs:
         uses: actions-rs/toolchain@v1.0.7
         with:
           profile: minimal
-          toolchain: 1.64.0
+          toolchain: 1.81.0
           override: true
           components: rustfmt, clippy