Revert "lib: init flakes.nix"

This reverts commit PR #167947.

Flakes aren't standardised and the `lib` namespace shouldn't be
polluted with utilities that serve only experimental uses.

lib/tests/misc.nix

@@ -22,16 +22,6 @@ in
 
 runTests {
 
-# FLAKES
-
-  testCallLocklessFlake = {
-    expr = callLocklessFlake {
-      path = ./flakes/subflakeTest;
-      inputs = { subflake = ./flakes/subflakeTest/subflake; inherit callLocklessFlake; };
-    };
-    expected = { x = 1; outPath = ./flakes/subflakeTest; };
-  };
-
 # TRIVIAL
 
   testId = {