Fix MacOS conditional build in telemetry::process (#1023)

On MacOS, the module `telemetry::process` in `linkerd-app-core` fails
to build because the `info!` macro is used on non-Linux systems, but
it is not imported.

Signed-off-by: Rahul Muttineni <rahulmutt@gmail.com>

Author: rahulmutt

linkerd/app/core/src/telemetry/process.rs

@@ -25,7 +25,7 @@ impl Report {
             .as_secs();
 
         #[cfg(not(target_os = "linux"))]
-        info!("System-level metrics are only supported on Linux");
+        tracing::info!("System-level metrics are only supported on Linux");
         Self {
             start_time: Arc::new(t0.into()),