Use python3 for wasm build

Author: workingjubilee

ci/docker/wasm32-unknown-unknown/Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get update -y && apt-get install -y --no-install-recommends \
   git \
   libc6-dev \
   make \
-  python \
+  python-is-python3 \
   xz-utils
 
 # Install `wasm2wat`