Adjust non-UTF-8 error message.

This commit came after the "Release 1.0.2" commit but I will include it
in 1.0.2 by cutting the release from this commit.

src/main.rs

@@ -146,7 +146,7 @@ where
     for reader in readers {
         for line in reader.lines() {
             let Ok(line) = line else {
-                eprintln!("error: non-UTF-8 input detected");
+                eprintln!("counts: non-UTF-8 input detected, aborting");
                 std::process::exit(1);
             };
             let (line, weight) = get_line_and_weight(line);

tests/cli.rs

@@ -228,7 +228,7 @@ baz 23 - +1
 #[test]
 fn non_utf8() -> Result<(), Box<dyn std::error::Error>> {
     let input = unsafe { std::str::from_utf8_unchecked(&[0x97, 0x98, 0x99, 0xff]) };
-    let expected_output = "error: non-UTF-8 input detected\n";
+    let expected_output = "counts: non-UTF-8 input detected, aborting\n";
 
     bad_test(input, expected_output)
 }