Improve wording in error handling guide

The original blog post referred to examples by their file names, and now
that it's in guide form, there is no file name. So edit the text so that
it makes a bit more sense.

Fixes #28428

src/doc/trpl/error-handling.md

@@ -182,7 +182,7 @@ analysis is the only way to get at the value stored inside an `Option<T>`. This
 means that you, as the programmer, must handle the case when an `Option<T>` is
 `None` instead of `Some(t)`.
 
-But wait, what about `unwrap` used in [`unwrap-double`](#code-unwrap-double)?
+But wait, what about `unwrap`,which we used [`previously`](#code-unwrap-double)?
 There was no case analysis there! Instead, the case analysis was put inside the
 `unwrap` method for you. You could define it yourself if you want:
 
@@ -211,7 +211,7 @@ that makes `unwrap` ergonomic to use. Unfortunately, that `panic!` means that
 
 ### Composing `Option<T>` values
 
-In [`option-ex-string-find`](#code-option-ex-string-find)
+In an [example from before](#code-option-ex-string-find),
 we saw how to use `find` to discover the extension in a file name. Of course,
 not all file names have a `.` in them, so it's possible that the file name has
 no extension. This *possibility of absence* is encoded into the types using