Remove spurious `@class` tags in two files

Remove spurious `@class` tags in two files

This was only used in two PHP files in all of core. It is not
needed (the block above the class keyword is naturally for that
class) and only emits a warning from Doxygen:

> PHPVersionCheck.php:35: warning: missing argument after \class.
> SpecialPageData.php:28: warning: missing argument after \class.

This is unlike JSDuck, where it is used to differentiate a function
from a constructor/class.

In Doxygen, `@class` is only used to create a virtual class within
the docs that isn't explicitly in an indexed file, and thus
requires a name.

Bug: T232104
Change-Id: Ie504a8e2b72be8f370dc0c90da6a03f64d93df2d