Correct example doc attribute

Author: Robin Kruppe

src/doc/reference.md

@@ -91,7 +91,7 @@ comments beginning with exactly one repeated asterisk in the block-open
 sequence (`/**`), are interpreted as a special syntax for `doc`
 [attributes](#attributes). That is, they are equivalent to writing
 `#[doc="..."]` around the body of the comment (this includes the comment
-characters themselves, i.e. `/// Foo` turns into `#[doc="/// Foo"]`).
+characters themselves, i.e. `/// Foo` turns into `#[doc="Foo"]`).
 
 Line comments beginning with `//!` and block comments beginning with `/*!` are
 doc comments that apply to the parent of the comment, rather than the item