nixosTest.lvm2: remove 4.19 kernel, test on 6.6

All tests continue to pass except for `nixosTests.lvm2.lvm-raid-sd-stage-1-linux-5_15` which continues to fail due to not having a kernel with the appropriate options configured.

nixos/tests/lvm2/default.nix

···
   pkgs ? import ../../.. { inherit system config; },
   lib ? pkgs.lib,
   kernelVersionsToTest ? [
-    "4.19"
     "5.4"
     "5.10"
     "5.15"
     "6.1"
+    "6.6"
     "latest"
   ],
 }: