chore: fix some comments (#494)

Signed-off-by: dashangcun <jchaodaohang@foxmail.com>
Co-authored-by: Toby Lawrence <tobz@users.noreply.github.com>

Author: dashangcun

metrics-util/src/quantile.rs

@@ -1,6 +1,6 @@
 /// A quantile that has both the raw value and a human-friendly display label.
 ///
-/// We work with quantiles for optimal floating-point precison over percentiles, but most of the
+/// We work with quantiles for optimal floating-point precision over percentiles, but most of the
 /// time, monitoring systems show us percentiles, and usually in an abbreviated form: `p99`.
 ///
 /// On top of holding the quantile value, we calculate the familiar "p99" style of label, doing the

metrics/src/cow.rs

@@ -226,7 +226,7 @@ where
 
         // SAFETY: We only ever hold a pointer to a borrowed value of at least the lifetime of
         // `Self`, or an owned value which we have ownership of (albeit indirectly when using
-        // `Arc<T>`), so our pointer is always valid and live for derefencing.
+        // `Arc<T>`), so our pointer is always valid and live for dereferencing.
         unsafe { borrowed_ptr.as_ref().unwrap() }
     }
 }

metrics/src/key.rs

@@ -19,7 +19,7 @@ impl KeyName {
         KeyName(SharedString::const_str(name))
     }
 
-    /// Gets a reference to the strin used for this name.
+    /// Gets a reference to the string used for this name.
     pub fn as_str(&self) -> &str {
         &self.0
     }