Remove CPU locking

This was already accidentally disabled in ba87b08. It also no longer
appears to be beneficial, and in fact slow things down, e.g. when
evaluating a NixOS system configuration:

  elapsed time:       median =      3.8170  mean =      3.8202  stddev =      0.0195  min =      3.7894  max =      3.8600  [rejected, p=0.00000, Δ=0.36929±0.02513]

1 files changed, 0 insertions, 9 deletions

diff --git a/src/libutil/affinity.hh b/src/libutil/affinity.hh
deleted file mode 100644
index c1bd28e13..000000000
--- a/src/libutil/affinity.hh
+++ /dev/null
@@ -1,9 +0,0 @@
-#pragma once
-
-namespace nix {
-
-void setAffinityTo(int cpu);
-int lockToCurrentCPU();
-void restoreAffinity();
-
-}