Improve method phpdoc for CRM_Utils_System

[braders]

Overview

The defacto standard for phpdoc comments states that when using @method to document static methods the return type must be specified: https://docs.phpdoc.org/guide/references/phpdoc/tags/method.html#method

By adding the return type void we can ensure that code editors such as VSCode can correctly hint methods against the CRM_Utils_System class.

Before

Missing return types on @method docs.

After

Return type void added as appropriate. Also a couple of minor formatting tweaks.

[civibot]

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[eileenmcnaughton]

thanks @braders - I agree these typehints really help when using an IDE