chore: remove unused common module

src/common.rs

@@ -1,15 +0,0 @@
-use std::io::Write;
-
-pub struct ProgramWriter {
-    stdin: std::process::ChildStdin,
-}
-
-impl Write for ProgramWriter {
-    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
-        self.stdin.write(buf)
-    }
-
-    fn flush(&mut self) -> std::io::Result<()> {
-        self.stdin.flush()
-    }
-}