chore: drop singleton connection limit on sqlite3 backend

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

database/database.go

@@ -45,14 +45,6 @@ func New(dialect, connection, defaultUser, defaultPass string, strength int, cre
 	// "too many connections", while load testing Gotify.
 	sqldb.SetMaxOpenConns(10)
 
-	if dialect == "sqlite3" {
-		// We use the database connection inside the handlers from the http
-		// framework, therefore concurrent access occurs. Sqlite cannot handle
-		// concurrent writes, so we limit sqlite to one connection.
-		// see https://github.com/mattn/go-sqlite3/issues/274
-		sqldb.SetMaxOpenConns(1)
-	}
-
 	if dialect == "mysql" {
 		// Mysql has a setting called wait_timeout, which defines the duration
 		// after which a connection may not be used anymore.