patch 9.0.0063: too many type casts for dict_get functions

Problem:    Too many type casts for dict_get functions.
Solution:   Change the key argument from "char_u *" to "char *".
diff --git a/src/insexpand.c b/src/insexpand.c
index c505158..7339ce9 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -2767,25 +2767,21 @@
     user_data.v_type = VAR_UNKNOWN;
     if (tv->v_type == VAR_DICT && tv->vval.v_dict != NULL)
     {
-	word = dict_get_string(tv->vval.v_dict, (char_u *)"word", FALSE);
-	cptext[CPT_ABBR] = dict_get_string(tv->vval.v_dict,
-						     (char_u *)"abbr", FALSE);
-	cptext[CPT_MENU] = dict_get_string(tv->vval.v_dict,
-						     (char_u *)"menu", FALSE);
-	cptext[CPT_KIND] = dict_get_string(tv->vval.v_dict,
-						     (char_u *)"kind", FALSE);
-	cptext[CPT_INFO] = dict_get_string(tv->vval.v_dict,
-						     (char_u *)"info", FALSE);
-	dict_get_tv(tv->vval.v_dict, (char_u *)"user_data", &user_data);
-	if (dict_get_string(tv->vval.v_dict, (char_u *)"icase", FALSE) != NULL
-			&& dict_get_number(tv->vval.v_dict, (char_u *)"icase"))
+	word = dict_get_string(tv->vval.v_dict, "word", FALSE);
+	cptext[CPT_ABBR] = dict_get_string(tv->vval.v_dict, "abbr", FALSE);
+	cptext[CPT_MENU] = dict_get_string(tv->vval.v_dict, "menu", FALSE);
+	cptext[CPT_KIND] = dict_get_string(tv->vval.v_dict, "kind", FALSE);
+	cptext[CPT_INFO] = dict_get_string(tv->vval.v_dict, "info", FALSE);
+	dict_get_tv(tv->vval.v_dict, "user_data", &user_data);
+	if (dict_get_string(tv->vval.v_dict, "icase", FALSE) != NULL
+				  && dict_get_number(tv->vval.v_dict, "icase"))
 	    flags |= CP_ICASE;
-	if (dict_get_string(tv->vval.v_dict, (char_u *)"dup", FALSE) != NULL)
-	    dup = dict_get_number(tv->vval.v_dict, (char_u *)"dup");
-	if (dict_get_string(tv->vval.v_dict, (char_u *)"empty", FALSE) != NULL)
-	    empty = dict_get_number(tv->vval.v_dict, (char_u *)"empty");
-	if (dict_get_string(tv->vval.v_dict, (char_u *)"equal", FALSE) != NULL
-			&& dict_get_number(tv->vval.v_dict, (char_u *)"equal"))
+	if (dict_get_string(tv->vval.v_dict, "dup", FALSE) != NULL)
+	    dup = dict_get_number(tv->vval.v_dict, "dup");
+	if (dict_get_string(tv->vval.v_dict, "empty", FALSE) != NULL)
+	    empty = dict_get_number(tv->vval.v_dict, "empty");
+	if (dict_get_string(tv->vval.v_dict, "equal", FALSE) != NULL
+				  && dict_get_number(tv->vval.v_dict, "equal"))
 	    flags |= CP_EQUAL;
     }
     else