correct new url to schema

Author: Emmanuelle-Morlock

tests/data/source/5.1.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<?xml-model href="https://epidoc.stoa.org/schema/8.23/tei-epidoc.rng" schematypens="http://relaxng.org/ns/structure/1.0"?><?xml-model href="http://www.stoa.org/epidoc/schema/8.23/tei-epidoc.rng" schematypens="http://purl.oclc.org/dsdl/schematron"?>
+<?xml-model href="https://epidoc.stoa.org/schema/8.23/tei-epidoc.rng" schematypens="https://relaxng.org/ns/structure/1.0"?>
+<?xml-model href="https://epidoc.stoa.org/schema/8.23/tei-epidoc.rng" schematypens="https://purl.oclc.org/dsdl/schematron"?>
 <!--<?xml-model href="http://www.stoa.org/epidoc/local/ircyr-checking.sch" schematypens="http://purl.oclc.org/dsdl/schematron"?>-->
 <TEI xmlns="http://www.tei-c.org/ns/1.0" xmlns:xi="http://www.w3.org/2001/XInclude">
    <teiHeader>