update PUK default + length

Author: alexgithublab

source/components/nitrokeys/features/piv/access_control.rst

@@ -46,10 +46,10 @@ Personal Unblocking Key (PUK)
 -----------------------------
 
 The *PUK* is used for management operations, such as unblocking the PIN.
-The factory default for the *PUK* is ``123456``.
+The factory default for the *PUK* is ``12345678``.
 
 .. note::
-   The *PUK* must have a maximal length of 8 characters.
+   The *PUK* must be 8 characters long.
    It can contain alphanumeric characters, including special characters such as punctations.
 
 .. warning::