Remove unnecessary invalidation from processing instructions

These invalidations only need to happen when elements are added,
removed, or manipulated. Processing instructions are not elements and
their contents are just text.

Author: nielsdos

ext/dom/processinginstruction.c

@@ -118,8 +118,6 @@ int dom_processinginstruction_data_write(dom_object *obj, zval *newval)
 	ZEND_ASSERT(Z_TYPE_P(newval) == IS_STRING);
 	zend_string *str = Z_STR_P(newval);
 
-	php_libxml_invalidate_node_list_cache_from_doc(nodep->doc);
-
 	xmlNodeSetContentLen(nodep, (xmlChar *) ZSTR_VAL(str), ZSTR_LEN(str));
 
 	return SUCCESS;