Simplify MemoryStats fetching

tracing-trace/src/entry.rs

@@ -121,6 +121,11 @@ impl MemoryStats {
         }
     }
 
+    #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+    pub fn fetch() -> Option<Self> {
+        None
+    }
+
     pub fn checked_sub(self, other: Self) -> Option<Self> {
         Some(Self { resident: self.resident.checked_sub(other.resident)? })
     }

tracing-trace/src/layer.rs

@@ -96,14 +96,8 @@ impl TraceLayer {
         self.start_time.elapsed()
     }
 
-    #[cfg(any(target_os = "linux", target_os = "macos"))]
     fn memory_stats(&self) -> Option<MemoryStats> {
-        Some(MemoryStats::fetch().unwrap())
-    }
-
-    #[cfg(not(any(target_os = "linux", target_os = "macos")))]
-    fn memory_stats(&self) -> Option<MemoryStats> {
-        None
+        MemoryStats::fetch()
     }
 
     fn send(&self, entry: Entry) {