[uWebsockets.js] Use Node 20 (#8426)

frameworks/JavaScript/uwebsockets.js/uwebsockets.js-postgres.dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-slim
+FROM node:20-slim
 
 COPY ./ ./
 

frameworks/JavaScript/uwebsockets.js/uwebsockets.js.dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-slim
+FROM node:20-slim
 
 COPY ./ ./