UPGRADING.INTERNALS: remove extra 's' [skip ci]

Author: DanielEScherzer

UPGRADING.INTERNALS

@@ -129,7 +129,7 @@ PHP 8.6 INTERNALS UPGRADE NOTES
     zend_reflection_property_set_raw_value() to expose the functionality of
     ReflectionProperty::setRawValueWithoutLazyInitialization() and
     ReflectionProperty::setRawValue() to C extensions.
-  . zend_argument_error_variadic() now takes a new 'function' parameters.
+  . zend_argument_error_variadic() now takes a new 'function' parameter.
   . Added zend_argument_error_ex(), zend_argument_type_error_ex(),
     zend_argument_value_error_ex().
   . Added zend_ast_dup().