subscriber: dim Compact targets, matching the default formatter (to…

…kio-rs#2409)

## Motivation

Fixes tokio-rs#2408

## Solution

Just switch to use `dim`

Before:
![2022-12-08_13-58-40](https://user-images.githubusercontent.com/623453/206576169-63ee4e20-b56f-4c63-a9b3-80ba2e97eec9.png)
After:
![2022-12-08_13-55-36](https://user-images.githubusercontent.com/623453/206576055-878d360f-7b95-4e18-bc31-4fb6f1b71a3a.png)
Full mode for comparison:
![2022-12-08_13-55-48](https://user-images.githubusercontent.com/623453/206576054-6e38852c-cb3a-4b84-98e5-50463cdb5073.png)

tracing-subscriber/src/fmt/format/mod.rs

@@ -2053,7 +2053,7 @@ pub(super) mod test {
         #[cfg(feature = "ansi")]
         #[test]
         fn with_ansi_true() {
-            let expected = "\u{1b}[2mfake time\u{1b}[0m \u{1b}[32m INFO\u{1b}[0m \u{1b}[1mtracing_subscriber::fmt::format::test\u{1b}[0m\u{1b}[2m:\u{1b}[0m hello\n";
+            let expected = "\u{1b}[2mfake time\u{1b}[0m \u{1b}[32m INFO\u{1b}[0m \u{1b}[2mtracing_subscriber::fmt::format::test\u{1b}[0m\u{1b}[2m:\u{1b}[0m hello\n";
             test_ansi(true, expected, crate::fmt::Subscriber::builder().compact())
         }