Use Node 20

Backported from the 2.6 branch.
Also, update composer & node deps.

docker/php/Dockerfile

@@ -1,7 +1,7 @@
 FROM php:8.1-fpm AS rootless
 
 ARG DEBIAN_FRONTEND=noninteractive
-ARG NODE_VERSION=16
+ARG NODE_VERSION=20
 
 RUN apt-get update \
     && apt-get install -y \
@@ -33,8 +33,7 @@ RUN apt-get update && apt-get install -y \
         zlib1g-dev \
         git \
         build-essential \
-        nodejs \
-        npm
+        nodejs
 RUN docker-php-ext-configure gd --with-freetype --with-jpeg --with-webp
 RUN docker-php-ext-install -j "$(nproc)" \
         bcmath \