Update Dockerfile

Co-authored-by: Andrew Ferrazzutti <andrewf@element.io>

Author: jaywink

Dockerfile

@@ -1,5 +1,5 @@
 # Build node-purple, which needs Debian for Python
-FROM node:22-bookworm as builder
+FROM node:22-bookworm AS builder
 COPY ./package.json ./package.json
 COPY ./yarn.lock ./yarn.lock
 COPY ./src ./src