Updated docker base image to node:18-bullseye in browser.Dockerfile

Resolves #345

`node:16-bullseye` seems outdated and resulted in the bug documented in the above issue.  It is not currently supported on the official list of node docker images:
https://hub.docker.com/_/node

The issue at #345 was resolved even by changing to `node:18-bullseye` only in the `build-stage`, but presumably it should be already upgraded also in the `production-stage`, so this commit/PR also updates the production stage based image.

Author: dannaf

browser.Dockerfile

@@ -1,5 +1,5 @@
 # Builder stage
-FROM node:16-bullseye as build-stage
+FROM node:18-bullseye as build-stage
 
 # install required tools to build the application
 RUN apt-get update && apt-get install -y libxkbfile-dev libsecret-1-dev
@@ -26,7 +26,7 @@ RUN yarn --pure-lockfile && \
     rm -r .git applications/electron theia-extensions/launcher theia-extensions/updater node_modules
 
 # Production stage uses a small base image
-FROM node:16-bullseye-slim as production-stage
+FROM node:18-bullseye-slim as production-stage
 
 # Create theia user and directories
 # Application will be copied to /home/theia