remove unnecessary emphasis in doc comment

During review of the previous commit, @joshtriplett noticed that
the emphasis on 'the same' is unnecessary. For consistency, remove it
on the offset() functions, as well.

Author: jannic

src/libcore/ptr.rs

@@ -1037,7 +1037,7 @@ impl<T: ?Sized> *const T {
     /// Behavior:
     ///
     /// * Both the starting and resulting pointer must be either in bounds or one
-    ///   byte past the end of *the same* allocated object.
+    ///   byte past the end of the same allocated object.
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
     ///
@@ -1657,7 +1657,7 @@ impl<T: ?Sized> *mut T {
     /// Behavior:
     ///
     /// * Both the starting and resulting pointer must be either in bounds or one
-    ///   byte past the end of *the same* allocated object.
+    ///   byte past the end of the same allocated object.
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
     ///