Remove AttributesSniff to fix conflict with Slevomat ReferenceUsedNamesOnly (#43)

The AttributesSniff required FQCN (fully qualified class names) for PHP 8
attributes, e.g. `#[\PHPUnit\Framework\Attributes\DataProvider('foo')]`.

However, this conflicts with SlevomatCodingStandard.Namespaces.ReferenceUsedNamesOnly
which requires using short names via use statements.

When both rules are active, the auto-fixer enters an infinite loop:
1. AttributesSniff converts to FQCN
2. ReferenceUsedNamesOnly converts back to short name with use statement
3. Go to step 1

Removing the AttributesSniff resolves this conflict and aligns with the
modern PHP convention of using short names with use statements for better
readability and IDE support.

Author: dereuromark