Fixed Procfile.dev to remove unnecessary empty line and terminated with a newline

[okonomi]

Fixed contents of Procfile.dev generated when executing rails new new_app -j esbuild --css tailwind.

before(without newline terminated):

web: bin/rails server -p 3000
js: yarn build --watch

css: yarn build:css --watch

after(with newline terminated):

web: bin/rails server -p 3000
js: yarn build --watch
css: yarn build:css --watch