Small refactor of doc/development/README.md

- Fix wrong doc_styleguide URL
- Clarify migrations refer to SQL
- Capitalize CSS

doc/development/README.md

@@ -8,14 +8,13 @@
 
 ## Styleguides
 
-- [Documentation styleguide](development/doc_styleguide.md) Use this styleguide if you are
+- [Documentation styleguide](doc_styleguide.md) Use this styleguide if you are
   contributing to documentation.
-- [Migration Style Guide](migration_style_guide.md) for creating safe migrations
+- [SQL Migration Style Guide](migration_style_guide.md) for creating safe SQL migrations
 - [Testing standards and style guidelines](testing.md)
-- [UI guide](ui_guide.md) for building GitLab with existing css styles and elements
+- [UI guide](ui_guide.md) for building GitLab with existing CSS styles and elements
 - [SQL guidelines](sql.md) for SQL guidelines
 
-
 ## Process
 
 - [Code review guidelines](code_review.md) for reviewing code and having code reviewed.