patch 8.2.3474: some places use "Vimscript" instead of "Vim script"

Problem:    Some places use "Vimscript" instead of "Vim script".
Solution:   Consistently use "Vim script". (Hirohito Higashi, closes #8910)
diff --git a/src/if_lua.c b/src/if_lua.c
index a131037..34eee8e 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -1853,7 +1853,7 @@
 	// Update the key
 	typval_T	tv;
 
-	// Convert the lua value to a vimscript type in the temporary variable
+	// Convert the lua value to a Vim script type in the temporary variable
 	lua_pushvalue(L, 4);
 	if (luaV_totypval(L, -1, &tv) == FAIL)
 	    return luaL_error(L, "Couldn't convert lua value");