Fix highlighting for mostly SQL block

When using Rouge's Console lexer it expects all ignored line breaks to
be proceeded by a backslash. In this code block as we are switching to
Mysql's command line which doesn't need a backslash. This leads to the
lexer breaking and all the lines ending up in a confusing mess.

However the sql syntax actually works much better for this block
anyway.

This line here shows why what we were trying to do wouldn't work with
Rouge:
844c0eeddf/lib/rouge/lexers/console.rb (L106)

guides/source/development_dependencies_install.md

@@ -156,7 +156,7 @@ required for running Active Record tests.
 
 In order to be able to run the test suite against MySQL you need to create a user named `rails` with privileges on the test databases:
 
-```bash
+```sql
 $ mysql -uroot -p
 
 mysql> CREATE USER 'rails'@'localhost';