env/windows-arm64: update VNC port in documentation

This change updates the VNC port in the documentation.

Change-Id: Iadffb0aa5cdc4f61734dd25400d09279204d5ca3
Reviewed-on: https://go-review.googlesource.com/c/build/+/325698
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
diff --git a/env/windows-arm64/README.md b/env/windows-arm64/README.md
index d0ad574..996c041 100644
--- a/env/windows-arm64/README.md
+++ b/env/windows-arm64/README.md
@@ -16,10 +16,10 @@
       qemu-image convert -O qcow2 win.vhdx win.qcow2
       ```
 
-- SSH to your instance tunneling port 5901, and run `win10-arm64.sh`
+- SSH to your instance tunneling port 5903, and run `win10-arm64.sh`
   script to boot the Windows VM.
     - You may need to stop the current VM: `sudo systemctl stop qemu`
-- VNC to the tunneled port 5901.
+- VNC to the tunneled port 5903.
 - Open the device control panel, and use the "Search for Drivers"
   button to search the virtio drive `D:` for drivers.
     - Matching drivers will be automatically installed.