snapcraft.yaml: set assumes to snapd 2.62

The new unconfined-mode attribute for the lxd-support interface is
only available in snapd 2.62 so ensure we depend on this version
of snapd.

Signed-off-by: Alex Murray <alex.murray@canonical.com>

snapcraft.yaml

@@ -1,7 +1,7 @@
 name: lxd
 base: core22
 assumes:
-  - snapd2.61
+  - snapd2.62
 version: git
 grade: devel
 summary: LXD - container and VM manager