linux_testing_bcachefs: fix meta

kernel.override overrides the invocation of buildLinux, not the
function in the file that defines the specific kernel version, so we
need to pass the arguments that buildLinux expects.

pkgs/os-specific/linux/kernel/linux-testing-bcachefs.nix

@@ -12,14 +12,12 @@
 
 # NOTE: bcachefs-tools should be updated simultaneously to preserve compatibility
 (kernel.override ( args // {
-  argsOverride = {
-    version = "${kernel.version}-bcachefs-unstable-${commitDate}";
+  version = "${kernel.version}-bcachefs-unstable-${commitDate}";
 
-    extraMeta = {
-      branch = "master";
-      maintainers = with lib.maintainers; [ davidak Madouura pedrohlc ];
-    };
-  } // argsOverride;
+  extraMeta = {
+    branch = "master";
+    maintainers = with lib.maintainers; [ davidak Madouura pedrohlc ];
+  };
 
   kernelPatches = [ {
       name = "bcachefs-${currentCommit}";