Fix sendmail error

Since using a systemd user to run budget, sendmail is failing with:

```
warning: mail_queue_enter: create file maildrop/665739.29050: Permission denied
```

Try specifying the complete path, as mentioned in:
https://github.com/NixOS/nixpkgs/issues/90248

1 files changed, 2 insertions, 1 deletions

diff --git a/src/mail.rs b/src/mail.rs
index dec8691..9fe0ed8 100644
--- a/src/mail.rs
+++ b/src/mail.rs
@@ -38,7 +38,8 @@ pub async fn send(
             .map(|r| r.address)
             .collect::<Vec<String>>();
 
-        let mut command = Command::new("sendmail");
+        // https://github.com/NixOS/nixpkgs/issues/90248
+        let mut command = Command::new("/run/wrappers/bin/sendmail");
         command.kill_on_drop(true);
         command.arg("-f").arg(FROM_ADDRESS);
         command.arg("--").args(recipient_addresses);