Try to fix libxml 2.9.12 tests

The test expectations here were for PHP 8.0, try to adjust them
for PHP 7.4.

ext/libxml/tests/bug61367-read_2.phpt

@@ -57,4 +57,4 @@ bool(true)
 
 Warning: DOMDocument::loadXML(): I/O warning : failed to load external entity "file:///%s/test_bug_61367-read/bad" in %s on line %d
 
-Warning: Attempt to read property "nodeValue" on null in %s on line %d
+Notice: Trying to get property 'nodeValue' of non-object in %s on line %d

ext/libxml/tests/libxml_disable_entity_loader_2.phpt

@@ -34,8 +34,6 @@ echo "Done\n";
 ?>
 --EXPECTF--
 bool(true)
-
-Deprecated: Function libxml_disable_entity_loader() is deprecated in %s on line %d
 bool(false)
 
 Warning: DOMDocument::loadXML(): I/O warning : failed to load external entity "%s" in %s on line %d