lenovo/thinkpad/l14/amd: update iommu comment

lenovo/thinkpad/l14/amd/default.nix

@@ -10,6 +10,10 @@
     # With BIOS version 1.12 and the IOMMU enabled, the amdgpu driver
     # either crashes or is not able to attach to the GPU depending on
     # the kernel version. I've seen no issues with the IOMMU disabled.
+    #
+    # BIOS version 1.13 claims to fix IOMMU issues, but we leave the
+    # IOMMU off to avoid a sad experience for those people that drew
+    # the short straw when they bought their laptop.
     "iommu=off"
   ];