Exemplar schema for ENRICH includes duplicate ids for Schematron constraint

[martindholmes]

This schema:

http://www.tei-c.org/Vault/P5/3.0.0/xml/tei/custom/schema/relaxng/tei_enrich.rng

contains the same id attribute value for two Schematron constraints:

tei_enrich-relatedItem-targetorcontent1-constraint-8

This was reported as a bug on the oxygen-tei repo by Alex at Oxygen (TEIC/oxygen-tei#7). The schema still validates, but if you try to use it to validate a document, validation fails at the Schematron stage due to the duplicate id.

[hcayless]

This is now fixed.