chore: remove Emulator struct

src/bus.rs

@@ -19,7 +19,7 @@ pub struct Bus {
     var_ram: VariableWorkRam,
     timer: Timer,
     int: Interrupt,
-    apu: Apu,
+    pub(crate) apu: Apu,
     high_ram: HighRam,
     serial: Serial,
     pub(crate) joyp: Joypad,
@@ -89,11 +89,6 @@ impl Bus {
             self.oam_write_byte(dest_addr, byte);
         }
     }
-
-    #[inline]
-    pub(crate) fn apu_mut(&mut self) -> &mut Apu {
-        &mut self.apu
-    }
 }
 
 impl Bus {