ci: use github-runner own rust toolchain instead of ai-user path

.github/workflows/release.yml

@@ -17,11 +17,11 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Set up Rust
-        run: echo "/home/ai-user/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/bin" >> $GITHUB_PATH
+        run: echo "$HOME/.cargo/bin" >> $GITHUB_PATH
 
       - name: Build release binary
         run: |
-          RUSTUP_HOME=/home/ai-user/.rustup cargo build --release --package nora-registry
+          cargo build --release --package nora-registry
           cp target/release/nora ./nora
 
       - name: Upload binary