Everywhere: Switch from (void) to [[maybe_unused]] (#4473)

Problem:
- `(void)` simply casts the expression to void. This is understood to
  indicate that it is ignored, but this is really a compiler trick to
  get the compiler to not generate a warning.

Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.

Note:
- Functions taking a `(void)` argument list have also been changed to
  `()` because this is not needed and shows up in the same grep
  command.

1 files changed, 1 insertions, 2 deletions

diff --git a/Applications/Piano/RollWidget.cpp b/Applications/Piano/RollWidget.cpp
index 9d99f1b67c..e6c655aa44 100644
--- a/Applications/Piano/RollWidget.cpp
+++ b/Applications/Piano/RollWidget.cpp
@@ -204,9 +204,8 @@ void RollWidget::mousemove_event(GUI::MouseEvent& event)
     update();
 }
 
-void RollWidget::mouseup_event(GUI::MouseEvent& event)
+void RollWidget::mouseup_event([[maybe_unused]] GUI::MouseEvent& event)
 {
-    (void)event;
     m_note_drag_start = {};
     m_note_drag_location = {};
 }