"classish"_exists() functions are not pure

These functions all trigger autoloading which may have the effect
of definining one or more new symbols. Note this does not apply
to `function_exists()` as there is no function autoloading.

Author: cs278

Core/Core.php

@@ -444,7 +444,6 @@ function property_exists($object_or_class, string $property): bool {}
  * @link https://secure.php.net/manual/en/function.trait-exists.php
  * @since 5.4
  */
-#[Pure(true)]
 function trait_exists(string $trait, bool $autoload = true): bool {}
 
 /**
@@ -459,7 +458,6 @@ function trait_exists(string $trait, bool $autoload = true): bool {}
  * @return bool true if <i>class_name</i> is a defined class,
  * false otherwise.
  */
-#[Pure(true)]
 function class_exists(string $class, bool $autoload = true): bool {}
 
 /**
@@ -475,7 +473,6 @@ function class_exists(string $class, bool $autoload = true): bool {}
  * <i>interface_name</i> has been defined, false otherwise.
  * @since 5.0.2
  */
-#[Pure(true)]
 function interface_exists(string $interface, bool $autoload = true): bool {}
 
 /**
@@ -507,7 +504,6 @@ function function_exists(string $function): bool {}
  * false otherwise.
  * @since 8.1
  */
-#[Pure(true)]
 function enum_exists(string $enum, bool $autoload = true): bool {}
 
 /**