Bump wal-g version to v2.0.0-rc1

This enables support for eks iam role authentication.

See:

- wal-g/wal-g#1209
- zalando/postgres-operator#1124 (comment)

postgres-appliance/Dockerfile

@@ -343,7 +343,7 @@ RUN export DEBIAN_FRONTEND=noninteractive \
 # Install patroni, wal-e and wal-g
 ENV PATRONIVERSION=2.1.1
 ENV WALE_VERSION=1.1.1
-ENV WALG_VERSION=v1.1
+ENV WALG_VERSION=v2.0.0-rc1
 RUN export DEBIAN_FRONTEND=noninteractive \
     && set -ex \
     && BUILD_PACKAGES="python3-pip python3-wheel python3-dev git patchutils binutils" \