Remove nolint annotations for unix errno comparisons

golangci-lint v1.54.2 comes with errorlint v1.4.4, which contains
the fix [1] whitelisting all errno comparisons for errors coming from
x/sys/unix.

Thus, these annotations are no longer necessary. Hooray!

[1] https://github.com/polyfloyd/go-errorlint/pull/47
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

signals.go

@@ -124,7 +124,7 @@ func (h *signalHandler) reap() (exits []exit, err error) {
 	for {
 		pid, err := unix.Wait4(-1, &ws, unix.WNOHANG, &rus)
 		if err != nil {
-			if err == unix.ECHILD { //nolint:errorlint // unix errors are bare
+			if err == unix.ECHILD {
 				return exits, nil
 			}
 			return nil, err