message: [docs.rs] Fix incorrect environment variable
diff: @@ -32,7 +32,8 @@ docker-compose build
  YOUR_CRATE=/path/to/your/crate
  # avoid docker-compose creating the volume if it doesn't exist
  if [ -e "$YOUR_CRATE" ]; then
  - docker-compose run -e DOCS_RS_LOCAL_IMAGE=build-env \
  + docker-compose run -e DOCS_RS_LOCAL_DOCKER_IMAGE=build-env \
  + -e RUST_BACKTRACE=1 \
  -v "$YOUR_CRATE":/opt/rustwide/workdir \
  web build crate --local /opt/rustwide/workdir
  else
  @@ -51,7 +52,7 @@ Rerun the build and start the container; it should take much less time now:
  cd /path/to/crates-build-env
  docker build --tag build-env .
  cd /path/to/docs.rs
  -docker-compose run -e DOCS_RS_LOCAL_IMAGE=build-env \
  +docker-compose run -e DOCS_RS_LOCAL_DOCKER_IMAGE=build-env \
  -v "$YOUR_CRATE":/opt/rustwide/workdir \
  web build crate --local /opt/rustwide/workdir
  ```
  