Fix return type of SessionHandler::read()

Author: kocsismate

ext/session/session.stub.php

@@ -71,7 +71,7 @@ public function open(string $path, string $name);
     /** @return bool */
     public function close();
 
-    /** @return string */
+    /** @return string|false */
     public function read(string $id);
 
     /** @return bool */
@@ -107,7 +107,7 @@ public function open(string $path, string $name) {}
     /** @return bool */
     public function close() {}
 
-    /** @return string */
+    /** @return string|false */
     public function read(string $id) {}
 
     /** @return bool */

ext/session/session_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 8175feea632f2832e43d830e70dc9332377b9f22 */
+ * Stub hash: 88f428841bc3e12b949a3308d60eae80d87e563a */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_session_name, 0, 0, MAY_BE_STRING|MAY_BE_FALSE)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, name, IS_STRING, 1, "null")