Remove what was only there to move a commit

Two lines added to prove that changing this image makes everything standing on
it go stale. The proof worked and the lines were never meant to stay: nothing
reads MESH_RUNTIME.

Dockerfile

@@ -55,5 +55,3 @@ COPY package.json ./
 COPY --from=build /app/node_modules ./node_modules
 COPY --from=build /app/dist ./dist
 ENTRYPOINT ["node", "dist/main.js"]
-# A real change, so the image itself moves and everything standing on it should be told.
-ENV MESH_RUNTIME=tools