Bug 11958: Fix typo in classification source help

Bug 11958: Fix typo in classification source help

The Classification Sources help file said the source was in the 942$2 but it's in the 952$2 and 94$2 so this patch fixes that.

To test:
* Go to Admin > Classification Sources
* Click Help
* Confirm the Help file is right now

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
String change, no errors.

Note: Perhaps change "Authorized Values ..." for "Authorized values ..."

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>