meson: drop duplicated condition

The generic check suffices for those four.
diff --git a/meson.build b/meson.build
index 31d73aa..865159c 100644
--- a/meson.build
+++ b/meson.build
@@ -3047,10 +3047,10 @@
         ['blkid'],
         ['dbus'],
         ['glib'],
-        ['nss-myhostname',   conf.get('ENABLE_NSS_MYHOSTNAME') == 1],
-        ['nss-mymachines',   conf.get('ENABLE_NSS_MYMACHINES') == 1],
-        ['nss-resolve',      conf.get('ENABLE_NSS_RESOLVE') == 1],
-        ['nss-systemd',      conf.get('ENABLE_NSS_SYSTEMD') == 1],
+        ['nss-myhostname'],
+        ['nss-mymachines'],
+        ['nss-resolve'],
+        ['nss-systemd'],
         ['hwdb'],
         ['tpm'],
         ['man pages',        want_man],