Linux 6.12 compat: META

Update the META file to reflect compatibility with the 6.12 kernel.

Reviewed-by: Umer Saleem <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes openzfs#16793

Author: behlendorf

Diff for: META

@@ -6,5 +6,5 @@ Release:       rc3
 Release-Tags:  relext
 License:       CDDL
 Author:        OpenZFS
-Linux-Maximum: 6.11
+Linux-Maximum: 6.12
 Linux-Minimum: 4.18