Fix invalid class/method declaration in stub

[sasezaki]

$ php -l stubs/SPL.phpstub
PHP Fatal error:  Abstract function SplHeap::compare() cannot contain body in stubs/SPL.phpstub on line 404
Errors parsing stubs/SPL.phpstub

This PR just fix above error in order to avoid confuse.

refs. PHP manual https://www.php.net/splheap

abstract class SplHeap

(Unexpectedly ? ) PHP-Parser can generate AST from uncompilable php code.

$ ./vendor/bin/php-parse -d '<?php abstract class A { protected abstract function compare() {}}'
====> Code <?php abstract class A { protected abstract function compare() {}}
==> Node dump:
array(
    0: Stmt_Class(
        attrGroups: array(
        )
        flags: MODIFIER_ABSTRACT (16)
        name: Identifier(
            name: A
        )
        extends: null
        implements: array(
        )
        stmts: array(
            0: Stmt_ClassMethod(
                attrGroups: array(
                )
                flags: MODIFIER_PROTECTED | MODIFIER_ABSTRACT (18)
                byRef: false
                name: Identifier(
                    name: compare
                )
                params: array(
                )
                returnType: null
                stmts: array(
                )
            )
        )
    )
)

[orklah]

Thanks!