Revert "update Ruby version to 4 in Dockerfile and devcontainer.json"

This reverts commit 0bdd85c.

Author: sireeshajonnalagadda

src/ruby-rails-postgres/.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-FROM mcr.microsoft.com/devcontainers/ruby:4-${templateOption:imageVariant}
+FROM mcr.microsoft.com/devcontainers/ruby:3-${templateOption:imageVariant}
 
 # Install Rails
 RUN su vscode -c "gem install rails webdrivers"

src/ruby/.devcontainer/devcontainer.json

@@ -3,7 +3,7 @@
 {
 	"name": "Ruby",
 	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "mcr.microsoft.com/devcontainers/ruby:4-${templateOption:imageVariant}"
+	"image": "mcr.microsoft.com/devcontainers/ruby:3-${templateOption:imageVariant}"
 
 	// Features to add to the dev container. More info: https://containers.dev/features.
 	// "features": {},