CI: switch to nodejs 14

.gitlab-ci/Dockerfile

@@ -11,7 +11,7 @@ RUN apt-get update && apt-get install -y \
     curl \
     && rm -rf /var/lib/apt/lists/*
 
-RUN curl -sL https://deb.nodesource.com/setup_12.x | bash - \
+RUN curl -sL https://deb.nodesource.com/setup_14.x | bash - \
     && rm -rf /var/lib/apt/lists/*
 
 RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -