Cleaned up long error description

Author: jwhite927

src/librustc_error_codes/error_codes/E0637.md

@@ -11,8 +11,7 @@ loop. The `_` character, which represents the ignore pattern, cannot be used
 as the identifier because it is a reserved lifetime name. To fix
 this, use a lowercase letter, or a series of lowercase letters as the lifetime
 identifier. Often a single lowercase letter, such as `'a`, is sufficient.  For
-more information, see
-[the book][bk-no].
+more information, see [the book][bk-no].
 
 Corrected underscore example:
 ```