MAINT: remove manual RUST installation in pipeline

.docker-base/Dockerfile

 # Use docker as parent image
-FROM docker:20.10.3
+FROM docker:20.10.18
 
 # http://bugs.python.org/issue19846
 ENV LANG C.UTF-8
@@ -11,32 +11,6 @@ RUN apk add --no-cache libffi-dev openssl-dev libc-dev libxslt libxslt-dev \
     libxml2 libxml2-dev
 RUN apk add --no-cache ca-certificates
 
-# install rust (needed for compiling a docker-compose dependency)
-# This is necessary until alpine comes with an up to date RUST
-# copied from https://github.com/rust-lang/docker-rust/blob/bbc7feb12033da3909dced4e88ddbb6964fbc328/1.50.0/alpine3.13/Dockerfile
-
-ENV RUSTUP_HOME=/usr/local/rustup \
-    CARGO_HOME=/usr/local/cargo \
-    PATH=/usr/local/cargo/bin:$PATH \
-    RUST_VERSION=1.50.0
-
-RUN set -eux; \
-    apkArch="$(apk --print-arch)"; \
-    case "$apkArch" in \
-        x86_64) rustArch='x86_64-unknown-linux-musl'; rustupSha256='05c5c05ec76671d73645aac3afbccf2187352fce7e46fc85be859f52a42797f6' ;; \
-        aarch64) rustArch='aarch64-unknown-linux-musl'; rustupSha256='6a8a480d8d9e7f8c6979d7f8b12bc59da13db67970f7b13161ff409f0a771213' ;; \
-        *) echo >&2 "unsupported architecture: $apkArch"; exit 1 ;; \
-    esac; \
-    url="https://static.rust-lang.org/rustup/archive/1.23.1/${rustArch}/rustup-init"; \
-    wget "$url"; \
-    echo "${rustupSha256} *rustup-init" | sha256sum -c -; \
-    chmod +x rustup-init; \
-    ./rustup-init -y --no-modify-path --profile minimal --default-toolchain $RUST_VERSION --default-host ${rustArch}; \
-    rm rustup-init; \
-    chmod -R a+w $RUSTUP_HOME $CARGO_HOME; \
-    rustup --version; \
-    cargo --version; \
-    rustc --version;
 
 
 RUN pip3 install wheel