Fix build badge

Signed-off-by: moson-mo <[email protected]>

README.md

@@ -2,7 +2,7 @@
 ## Simple GUI application for gocryptfs
 
 [![GitHub release](https://img.shields.io/github/v/tag/moson-mo/cryptor.svg?label=release&sort=semver)](https://github.com/moson-mo/cryptor/releases)
-[![build](https://img.shields.io/github/actions/workflow/status/moson-mo/cryptor/build.yml?branch=main)](https://github.com/moson-mo/cryptor/actions)
+[![build](https://img.shields.io/github/actions/workflow/status/moson-mo/cryptor/build.yml?branch=master)](https://github.com/moson-mo/cryptor/actions)
 
 cryptor is a simple GUI wrapper for [gocryptfs](https://github.com/rfjakob/gocryptfs), written in Vala using the GTK toolkit.  
 It allows you to create and mount gocryptfs encrypted file systems via a graphical user interface.