Use wasmtime nightlies (dev) when running tests in CI

The latest Rust toolchains have a wasm-tools that is too new for
released wasmtime versions.  So, for the moment, use nightlies.

Author: wingo

.github/workflows/compile-tests.yml

@@ -141,7 +141,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     needs: [build_assemblyscript, build_c, build_rust]
     env:
-      WASMTIME_VERSION: v39.0.1
+      WASMTIME_VERSION: dev
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest, windows-11-arm]