Fixed a typo in auth docs.

docs/topics/auth/passwords.txt

@@ -146,7 +146,7 @@ algorithm.
     that ``bcrypt(password_with_100_chars) == bcrypt(password_with_100_chars[:72])``.
     The original ``BCryptPasswordHasher`` does not have any special handling and
     thus is also subject to this hidden password length limit.
-    ``BCryptSHA256PasswordHasher`` fixes this by first first hashing the
+    ``BCryptSHA256PasswordHasher`` fixes this by first hashing the
     password using sha256. This prevents the password truncation and so should
     be preferred over the ``BCryptPasswordHasher``. The practical ramification
     of this truncation is pretty marginal as the average user does not have a