Remove trailing whitespace

doc/hash/reference.adoc

@@ -610,14 +610,14 @@ in the input translate to large changes in the returned hash code
 —ideally, flipping one bit in the representation of the input value results
 in each bit of the hash code flipping with probability 50%. Libraries
 such as link:../../../unordered/index.html[Boost.Unordered] consult this trait
-to determine if the supplied hash function is of high quality. 
+to determine if the supplied hash function is of high quality.
 `boost::hash` for `std::basic_string<Ch>` and `std::basic_string_view<Ch>`
 has this trait set to `true` when `Ch` is an integral type (this includes
 `std::string` and `std::string_view`, among others).
 Users can set this trait for a particular `Hash` type by:
 
 * Inserting the nested `is_avalanching` typedef in the class definition
-if they have access to its source code. 
+if they have access to its source code.
 * Writing a specialization of `boost::hash_is_avalanching`
 for `Hash`.