[Minor] Fix another misprint

src/plugins/lua/clickhouse.lua

@@ -53,7 +53,7 @@ local settings = {
   spf_reject_symbols = {'R_SPF_FAIL'},
   spf_dnsfail_symbols = {'R_SPF_DNSFAIL', 'R_SPF_PERMFAIL'},
   spf_neutral_symbols = {'R_DKIM_TEMPFAIL', 'R_DKIM_PERMFAIL'},
-  spf_na_symbol = {'R_SPF_NA'},
+  spf_na_symbols = {'R_SPF_NA'},
   stop_symbols = {},
   ipmask = 19,
   ipmask6 = 48,