Indent with four spaces instead of two

to adhere to the standard's best practice

and (hopefully) make the nesting carry over to being displayed in the rendered output

Author: shaedrich

docs/topics/defined-names.md

@@ -547,16 +547,16 @@ $this->spreadsheet->addDefinedName(
 The names that you assign to Defined Name must follow the following set of rules:
 
  - The first character of a name must be one of the following characters:
-   - letter (including UTF-8 letters)
-   - underscore (`_`)
+     - letter (including UTF-8 letters)
+     - underscore (`_`)
  - Remaining characters in the name can be
-   - letters (including UTF-8 letters)
-   - numbers (including UTF-8 numbers)
-   - periods (`.`)
-   - underscore characters (`_`)
+     - letters (including UTF-8 letters)
+     - numbers (including UTF-8 numbers)
+     - periods (`.`)
+     - underscore characters (`_`)
  - The following are not allowed:
-   - Space characters are not allowed as part of a name.
-   - Names can't look like cell addresses, such as A35 or R2C2
+     - Space characters are not allowed as part of a name.
+     - Names can't look like cell addresses, such as A35 or R2C2
  - Names are not case sensitive. For example, `North` and `NORTH` are treated as the same name.
 
 ### Limitations