input_common/input_mapping: Remove const from return value

Top-level const on a return by value can inhibit move semantics, and is
unnecessary.

src/input_common/input_mapping.cpp

@@ -19,7 +19,7 @@ void MappingFactory::BeginMapping(Polling::InputType type) {
     second_axis = -1;
 }
 
-[[nodiscard]] const Common::ParamPackage MappingFactory::GetNextInput() {
+Common::ParamPackage MappingFactory::GetNextInput() {
     Common::ParamPackage input;
     input_queue.Pop(input);
     return input;

src/input_common/input_mapping.h

@@ -20,7 +20,7 @@ public:
     void BeginMapping(Polling::InputType type);
 
     /// Returns an input event with mapping information from the input_queue
-    [[nodiscard]] const Common::ParamPackage GetNextInput();
+    [[nodiscard]] Common::ParamPackage GetNextInput();
 
     /**
      * Registers mapping input data from the driver

src/input_common/main.cpp

@@ -394,7 +394,7 @@ void InputSubsystem::BeginMapping(Polling::InputType type) {
     impl->mapping_factory->BeginMapping(type);
 }
 
-const Common::ParamPackage InputSubsystem::GetNextInput() const {
+Common::ParamPackage InputSubsystem::GetNextInput() const {
     return impl->mapping_factory->GetNextInput();
 }
 

src/input_common/main.h

@@ -126,7 +126,7 @@ public:
     void BeginMapping(Polling::InputType type);
 
     /// Returns an input event with mapping information.
-    [[nodiscard]] const Common::ParamPackage GetNextInput() const;
+    [[nodiscard]] Common::ParamPackage GetNextInput() const;
 
     /// Stop polling from all backends.
     void StopMapping() const;