Add missing dollar sign for bash script [skip ci]

railties/CHANGELOG.md

@@ -4,8 +4,8 @@
     defined by Active Record.
 
     ```bash
-    bin/rails generate model Post save
-    bin/rails generate model Post hash
+    $ bin/rails generate model Post save
+    $ bin/rails generate model Post hash
     ```
 
     *Petrik de Heus*
@@ -15,17 +15,17 @@
 *   Add ability to show slow tests to the test runner
 
     ```bash
-    bin/test --profile # additionally prints 10 (default) slowest tests
+    $ bin/test --profile # additionally prints 10 (default) slowest tests
     # or
-    bin/test --profile 20 # prints 20 slowest tests
+    $ bin/test --profile 20 # prints 20 slowest tests
     ```
 
     *fatkodima*
 
 *   `rails new --javascript` generator now supports Bun
 
     ```bash
-    rails new my_new_app --javascript=bun
+    $ rails new my_new_app --javascript=bun
     ```
 
     *Jason Meller*