Add "js" to tidy extra checks for "mingw-check-tidy" CI job

Also, stop pre-installing `eslint` - the docker image is not cached in CI, so there's no point in explicitly `npm install`ing it instead of just letting `npx` download it

Author: yotamofek

src/ci/docker/host-x86_64/mingw-check-tidy/Dockerfile

@@ -28,9 +28,6 @@ COPY scripts/nodejs.sh /scripts/
 RUN sh /scripts/nodejs.sh /node
 ENV PATH="/node/bin:${PATH}"
 
-# Install eslint
-COPY host-x86_64/mingw-check-tidy/eslint.version /tmp/
-
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
@@ -41,9 +38,7 @@ RUN pip3 install --no-deps --no-cache-dir --require-hashes -r /tmp/reuse-require
 COPY host-x86_64/mingw-check-1/validate-toolstate.sh /scripts/
 COPY host-x86_64/mingw-check-1/validate-error-codes.sh /scripts/
 
-RUN bash -c 'npm install -g eslint@$(cat /tmp/eslint.version)'
-
 # NOTE: intentionally uses python2 for x.py so we can test it still works.
 # validate-toolstate only runs in our CI, so it's ok for it to only support python3.
 ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 \
-    src/tools/tidy tidyselftest --extra-checks=py,cpp
+    src/tools/tidy tidyselftest --extra-checks=py,cpp,js