patch 8.1.1035: prop_remove() second argument is not optional

Problem:    prop_remove() second argument is not optional.
Solution:   Fix argument count.  Use "buf" instead of "curbuf". (closes #4147)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f5a0bd8..81264bd 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -788,7 +788,7 @@
     {"prop_add",	3, 3, f_prop_add},
     {"prop_clear",	1, 3, f_prop_clear},
     {"prop_list",	1, 2, f_prop_list},
-    {"prop_remove",	2, 3, f_prop_remove},
+    {"prop_remove",	1, 3, f_prop_remove},
     {"prop_type_add",	2, 2, f_prop_type_add},
     {"prop_type_change", 2, 2, f_prop_type_change},
     {"prop_type_delete", 1, 2, f_prop_type_delete},