fix BlueZ version
This change was not released until 5.51 (see https://github.com/bluez/bluez/commit/fa9473bcc48417d69cc9ef81d41a72b18e34a55a)
@@ -16,7 +16,7 @@ Special handling for ``write_gatt_char``
The ``type`` option to the ``Characteristic.WriteValue``
method was added to
-`Bluez in 5.50 <https://git.kernel.org/pub/scm/bluetooth/bluez.git/commit?id=fa9473bcc48417d69cc9ef81d41a72b18e34a55a>`_
+`Bluez in 5.51 <https://git.kernel.org/pub/scm/bluetooth/bluez.git/commit?id=fa9473bcc48417d69cc9ef81d41a72b18e34a55a>`_
Before that commit, ``Characteristic.WriteValue`` was only "Write with response".
``Characteristic.AcquireWrite`` was added in
