Jenkins/Docker: Update hadolint version.
- Ignore hadolint warnings about not pinned version.
diff --git a/docker/dockerfile.gnu b/docker/dockerfile.gnu
index dee7f4a..9c8e13e 100644
--- a/docker/dockerfile.gnu
+++ b/docker/dockerfile.gnu
@@ -6,6 +6,7 @@
 
 # install packages from official Ubuntu repo
 ENV DEBIAN_FRONTEND=noninteractive
+# hadolint ignore=DL3008
 RUN apt-get update && \
     apt-get install --no-install-recommends -y \
         bc \
@@ -48,6 +49,7 @@
 
 # install Python requirements
 COPY requirements.txt ${INSTALLER_PATH}/
+# hadolint ignore=DL3013
 RUN python3 -m pip install -U --no-cache-dir pip && \
     python3 -m pip install -U --no-cache-dir -r ${INSTALLER_PATH}/requirements.txt