Revert "fix(ci/cd): pin cargo-lambda back to 1.8.1 temporarily (awslabs#989)"

This reverts commit 57cd659.

Author: jlizen

.github/workflows/run-integration-test.yml

@@ -18,8 +18,6 @@ jobs:
             repo: cargo-lambda/cargo-lambda
             platform: linux
             arch: x86_64
-            # TODO: unpin once https://github.com/cargo-lambda/cargo-lambda/issues/856 is fixed
-            tag: v1.8.1
         - name: install Zig toolchain
           uses: korandoru/setup-zig@v1
           with: