fix: clippy issues

src/apu.rs

@@ -599,7 +599,7 @@ impl Apu {
     }
 
     pub fn ch1_enabled(&mut self) -> bool {
-        return self.ch1_out_enabled;
+        self.ch1_out_enabled
     }
 
     pub fn set_ch1_enabled(&mut self, enabled: bool) {
@@ -607,7 +607,7 @@ impl Apu {
     }
 
     pub fn ch2_enabled(&mut self) -> bool {
-        return self.ch2_out_enabled;
+        self.ch2_out_enabled
     }
 
     pub fn set_ch2_enabled(&mut self, enabled: bool) {
@@ -615,7 +615,7 @@ impl Apu {
     }
 
     pub fn ch3_enabled(&mut self) -> bool {
-        return self.ch3_out_enabled;
+        self.ch3_out_enabled
     }
 
     pub fn set_ch3_enabled(&mut self, enabled: bool) {
@@ -623,7 +623,7 @@ impl Apu {
     }
 
     pub fn ch4_enabled(&mut self) -> bool {
-        return self.ch4_out_enabled;
+        self.ch4_out_enabled
     }
 
     pub fn set_ch4_enabled(&mut self, enabled: bool) {