Dev docs: The system tests do not need elevated privileges after all.

docs/source/dev/README.rst

@@ -22,12 +22,9 @@ Unit tests are also run on CI.
 
 The system tests are run using this command::
 
-  $ sudo --preserve-env nix-build nixos/system-tests.nix
+  $ nix-build nixos/system-tests.nix
 
 The system tests boot QEMU VMs which prevents them from running on CI at this time.
-Starting VMs require elevated privileges,
-which is the reason for the suggested ``sudo`` command,
-together with the ``--preserve-env`` option to avoid escaping the ``nix-shell`` set up at the top.
 The build requires > 10 GB of disk space,
 and the VMs might be timing out on slow or busy machines.
 If you run into timeouts,
@@ -35,7 +32,7 @@ try `raising the number of retries <https://github.com/PrivateStorageio/PrivateS
 
 It is also possible go through the testing script interactively - useful for debugging::
 
-  $ sudo --preserve-env nix-build -A private-storage.driver nixos/system-tests.nix
+  $ nix-build -A private-storage.driver nixos/system-tests.nix
 
 This will give you a result symlink in the current directory.
 Inside that is bin/nixos-test-driver which gives you a kind of REPL for interacting with the VMs.