gnb: fix TDD period appconfig param comment

Author: frankist

apps/gnb/gnb_appconfig_cli11_schema.cpp

@@ -493,7 +493,8 @@ static void configure_cli11_tdd_ul_dl_pattern_args(CLI::App& app, tdd_ul_dl_patt
 {
   app.add_option("--dl_ul_tx_period",
                  pattern_params.dl_ul_period_slots,
-                 "TDD pattern periodicity in slots. Must be 0.5, 0.625, 1, 1.25, 2, 2.5, 5 or 10 milliseconds.")
+                 "TDD pattern periodicity in slots. The combination of this value and the chosen numerology must lead"
+                 " to a TDD periodicity of 0.5, 0.625, 1, 1.25, 2, 2.5, 5 or 10 milliseconds.")
       ->capture_default_str()
       ->check(CLI::Range(2, 80));
   app.add_option("--nof_dl_slots", pattern_params.nof_dl_slots, "TDD pattern nof. consecutive full DL slots")