Remove invalid UTF-8 file from repo, use temp file instead

tests/examples/test-invalid-utf8-�(.rs

@@ -1,4 +0,0 @@
-fn print_square(num: f64) {
-    let result = f64::powf(num, 2.0);
-    println!("The square of {:.2} is {:.2}.", num, result);
-}