reference: fix netplan url

doc/reference/autoinstall-reference.rst

@@ -196,11 +196,15 @@ search_drivers
 ~~~~~~~~~~~~~~
 
 * **type:** boolean
-* **default:** ``true``
+* **default:** ``true`` (mostly, see below)
 
 Whether the installer should search for available third-party drivers. When
 set to ``false``, it disables the drivers :ref:`screen and section<ai-drivers>`.
 
+The default is true for most installs but false when a "core boot" or
+"enhanced secure boot" method is selected (where third-party drivers
+cannot currently be installed).
+
 id
 ~~
 
@@ -218,7 +222,7 @@ network
 * **default:** DHCP on interfaces named ``eth*`` or ``en*``
 * **can be interactive:** yes
 
-`Netplan-formatted <https://netplan.io/reference>`_ network configuration.
+`Netplan-formatted <https://netplan.readthedocs.io/en/stable/netplan-yaml/>`_ network configuration.
 This will be applied during installation as well as in the installed system.
 The default is to interpret the config for the install media, which runs
 DHCPv4 on any interface with a name matching "``eth*``" or "``en*``" but then