[gnome-boxes] app: Drop unused source broker type method

[Felipe Borges <felipeborges src gnome org>]

commit 221b71c6a0aa2f5cf8301deb205eec66cb3f76e8
Author: Felipe Borges <felipeborges gnome org>
Date:   Tue Dec 14 14:37:12 2021 +0100

    app: Drop unused source broker type method
    
    Boxes now manages all its sources and this function doesn't need
    to be used anymore.

 src/app.vala | 4 ----
 1 file changed, 4 deletions(-)
---
diff --git a/src/app.vala b/src/app.vala
index 31d14b07..fd0d3bdd 100644
--- a/src/app.vala
+++ b/src/app.vala
@@ -155,10 +155,6 @@ public override void startup () {
         check_module_kvm_loaded.begin ();
     }
 
-    public bool has_broker_for_source_type (string type) {
-        return brokers.contains (type);
-    }
-
     public delegate void CallReadyFunc ();
     public void call_when_ready (owned CallReadyFunc func) {
         if (is_ready)