Remove restriction on method call inlining

In PHP 8, we are guaranteed that $this exists, so we no longer have
to forbid this case.

ext/opcache/Optimizer/optimize_func_calls.c

@@ -113,13 +113,6 @@ static void zend_try_inline_call(zend_op_array *op_array, zend_op *fcall, zend_o
 				return;
 			}
 
-			if (fcall->opcode == ZEND_INIT_METHOD_CALL && fcall->op1_type == IS_UNUSED) {
-				/* TODO: we can't inlne methods, because $this may be used
-				 *       not in object context ???
-				 */
-				return;
-			}
-
 			for (i = 0; i < num_args; i++) {
 				/* Don't inline functions with by-reference arguments. This would require
 				 * correct handling of INDIRECT arguments. */