fix: updated August short month name for id_ID locale

The August short month name in the Indonesian locale was initially set to be "Ags". But it was later shown that "Agu" was the preferrable abbreviation, as explained by an Indonesian linguist (ref 1.) and as shown on Wikipedia (ref 2.).

ref:
1. https://twitter.com/ivanlanin/status/1298795394562846723
2. https://id.wikipedia.org/wiki/Bulan_(penanggalan)

format_id_id.go

@@ -47,7 +47,7 @@ var shortMonthNamesIdID = map[string]string{
 	"May": "Mei",
 	"Jun": "Jun",
 	"Jul": "Jul",
-	"Aug": "Ags",
+	"Aug": "Agu",
 	"Sep": "Sep",
 	"Oct": "Okt",
 	"Nov": "Nov",