PHP 8.5: Replace deprecated (boolean) cast with (bool) in BoolDataType::getValue()

Problem/Motivation

On PHP 8.5, BoolDataType::getValue() triggers a deprecation because it uses the non-canonical (boolean) cast. PHP 8.5 deprecates the long-form scalar casts in favour of
their canonical short forms.

Deprecated: Non-canonical cast (boolean) is deprecated, use the (bool) cast instead in src/Plugin/search_api/data_type/BoolDataType.php on line 25

Root cause: BoolDataType::getValue() casts the value with (boolean) instead of (bool).

Steps to reproduce

1. Run on PHP 8.5 with a Typesense index that has a boolean field (the typesense_bool data type).
2. Index/transform content so BoolDataType::getValue() runs.
3. Observe the Deprecated: Non-canonical cast (boolean) ... notice (or as a deprecation under PHPUnit --display-deprecations).

Proposed resolution

Use the canonical (bool) cast.

   public function getValue($value): bool {
  -    return (boolean) $value;
  +    return (bool) $value;
     }

Remaining tasks

• Review the merge request.