All Write errors are fatal

With TLS connections a Write timeout caused by a SetDeadline permanently
breaks the connection. However, the errors are reported as temporary. So
there is no way to determine if it really is recoverable. As these were
the only kind of Write error that was recovered all Write errors are now
fatal to the connection.

https://github.com/jackc/pgx/issues/494
https://github.com/jackc/pgx/issues/506
https://github.com/golang/go/issues/29971

batch.go

@@ -133,11 +133,9 @@ func (b *Batch) Send(ctx context.Context, txOptions *TxOptions) error {
 		b.conn.pendingReadyForQueryCount++
 	}
 
-	n, err := b.conn.conn.Write(buf)
+	_, err = b.conn.conn.Write(buf)
 	if err != nil {
-		if fatalWriteErr(n, err) {
-			b.conn.die(err)
-		}
+		b.conn.die(err)
 		return err
 	}