Updated Docker docs to Node 20

Signed-off-by: Andre Wanlin <awanlin@spotify.com>

docs/deployment/docker.md

@@ -54,7 +54,7 @@ Once the host build is complete, we are ready to build our image. The following
 `Dockerfile` is included when creating a new app with `@backstage/create-app`:
 
 ```dockerfile
-FROM node:18-bookworm-slim
+FROM node:20-bookworm-slim
 
 # Set Python interpreter for `node-gyp` to use
 ENV PYTHON=/usr/bin/python3
@@ -175,7 +175,7 @@ the repo root:
 
 ```dockerfile
 # Stage 1 - Create yarn install skeleton layer
-FROM node:18-bookworm-slim AS packages
+FROM node:20-bookworm-slim AS packages
 
 WORKDIR /app
 COPY package.json yarn.lock ./
@@ -190,7 +190,7 @@ COPY plugins plugins
 RUN find packages \! -name "package.json" -mindepth 2 -maxdepth 2 -exec rm -rf {} \+
 
 # Stage 2 - Install dependencies and build packages
-FROM node:18-bookworm-slim AS build
+FROM node:20-bookworm-slim AS build
 
 # Set Python interpreter for `node-gyp` to use
 ENV PYTHON=/usr/bin/python3
@@ -230,7 +230,7 @@ RUN mkdir packages/backend/dist/skeleton packages/backend/dist/bundle \
     && tar xzf packages/backend/dist/bundle.tar.gz -C packages/backend/dist/bundle
 
 # Stage 3 - Build the actual backend image and install production dependencies
-FROM node:18-bookworm-slim
+FROM node:20-bookworm-slim
 
 # Set Python interpreter for `node-gyp` to use
 ENV PYTHON=/usr/bin/python3

docs/deployment/flightcontrol.md

@@ -28,7 +28,7 @@ The following two code snippets demonstrate this method. The first block of code
 # yarn build:backend
 #
 # Once the commands have been run, you can build the image using `yarn build-image`
-FROM node:18-bookworm-slim as build
+FROM node:20-bookworm-slim as build
 
 USER node
 WORKDIR /app
@@ -43,7 +43,7 @@ RUN yarn tsc
 # The configuration files here should match the one you use inside the Dockerfile below.
 RUN yarn build:backend --config ../../app-config.yaml
 
-FROM node:18-bookworm-slim
+FROM node:20-bookworm-slim
 
 # Install isolate-vm dependencies, these are needed by the @backstage/plugin-scaffolder-backend.
 RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \