libct/seccomp/patchbpf: rm duplicated code

In findLastSyscalls, we convert libseccomp.ArchNative to the real
libseccomp architecture, but archToNative already does that, so
this code is redundant.

Remove the redundant code, and move its comment to archToNative.

Fixes: 7a8d7162f
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/seccomp/patchbpf/enosys_linux.go

@@ -240,16 +240,6 @@ func findLastSyscalls(config *configs.Seccomp) (lastSyscallMap, error) {
 			return nil, fmt.Errorf("unable to validate seccomp architecture: %w", err)
 		}
 
-		// Map native architecture to a real architecture value to avoid
-		// doubling-up the lastSyscall mapping.
-		if arch == libseccomp.ArchNative {
-			nativeArch, err := libseccomp.GetNativeArch()
-			if err != nil {
-				return nil, fmt.Errorf("unable to get native architecture: %w", err)
-			}
-			arch = nativeArch
-		}
-
 		// Figure out native architecture representation of the architecture.
 		nativeArch, err := archToNative(arch)
 		if err != nil {