revert: atlas and precision change

Looks like Atlas (the new migration library under Ent) cannot
handle precision properly.

An issue has been reported to Ent: https://github.com/ent/ent/issues/2454

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

storage/ent/schema/dialects.go

@@ -15,7 +15,7 @@ var textSchema = map[string]string{
 }
 
 var timeSchema = map[string]string{
-	dialect.Postgres: "timestamptz(3)",
+	dialect.Postgres: "timestamptz",
 	dialect.SQLite:   "timestamp",
 	dialect.MySQL:    "datetime(3)",
 }