patch 8.2.4683: verbose check with dict_find() to see if a key is present

Problem:    Verbose check with dict_find() to see if a key is present.
Solution:   Add dict_has_key(). (Yegappan Lakshmanan, closes #10074)
diff --git a/src/search.c b/src/search.c
index 98241a4..a66075f 100644
--- a/src/search.c
+++ b/src/search.c
@@ -4878,7 +4878,7 @@
 		return;
 	    }
 	}
-	if (dict_find(d, (char_u *)"matchseq", -1) != NULL)
+	if (dict_has_key(d, "matchseq"))
 	    matchseq = TRUE;
     }