Fix help string of kf-max-pyr-height.

Bug: b/242914876
Change-Id: I9bb465d047d05c12378bf86a061dbd0e09548199
diff --git a/av1/arg_defs.c b/av1/arg_defs.c
index 7d1bbab..a954b88 100644
--- a/av1/arg_defs.c
+++ b/av1/arg_defs.c
@@ -674,8 +674,9 @@
               "to a given target level"),
   .kf_max_pyr_height = ARG_DEF(
       NULL, "kf-max-pyr-height", 1,
-      "Maximum height of pyrimid structure used for the GOP starting with a "
+      "Maximum height of pyramid structure used for the GOP starting with a "
       "key frame (-1 to 5). When set to -1 (default), it does not have any "
-      "effects. The height also obeys the value set to gf_max_pyr_height."),
+      "effect. The actual maximum pyramid height will be the minimum of this "
+      "value and the value of gf_max_pyr_height."),
 #endif  // CONFIG_AV1_ENCODER
 };