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.

Libraries/LibGfx/PBMLoader.cpp

@@ -118,10 +118,8 @@ static int read_number(Streamer& streamer)
     return sb.to_string().to_uint().value_or(0);
 }
 
-static bool read_comment(PBMLoadingContext& context, Streamer& streamer)
+static bool read_comment([[maybe_unused]] PBMLoadingContext& context, Streamer& streamer)
 {
-    (void)context;
-
     bool exist = false;
     u8 byte;