Normalize: Use float instead of double

I came across this in the PHP track docs:

> - Casts `(float)` and `(real)` are normalized to `(double)`

Was there a discussion about that anywhere? Because `double` is not seen by PHP as a type, it is seen as an alias for `float` only:

> (double) and (real) are aliases of the (float) cast. These casts do not use the canonical type name and are not recommended.

Througout the PHP documentation `float` is used as the type for floating point numbers.

See:

- https://www.php.net/manual/en/language.types.type-system.php
- https://www.php.net/manual/en/language.types.type-juggling.php#language.types.typecasting