Auto merge of #24067 - apasel422:patch-1, r=Gankro

Per [RFC #505](https://github.com/rust-lang/rfcs/blob/master/text/0505-api-comment-conventions.md#formatting).

Author: bors

src/libcore/convert.rs

@@ -21,15 +21,15 @@ use marker::Sized;
 /// A cheap, reference-to-reference conversion.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait AsRef<T: ?Sized> {
-    /// Perform the conversion.
+    /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn as_ref(&self) -> &T;
 }
 
 /// A cheap, mutable reference-to-mutable reference conversion.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait AsMut<T: ?Sized> {
-    /// Perform the conversion.
+    /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn as_mut(&mut self) -> &mut T;
 }
@@ -38,15 +38,15 @@ pub trait AsMut<T: ?Sized> {
 /// expensive.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Into<T>: Sized {
-    /// Perform the conversion.
+    /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn into(self) -> T;
 }
 
 /// Construct `Self` via a conversion.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait From<T> {
-    /// Perform the conversion.
+    /// Performs the conversion.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn from(T) -> Self;
 }