Do not check header license in xml files

Author: lopezzot

.pre-commit-config.yaml

@@ -36,4 +36,4 @@ repos:
         "-o", "Key4hep-Project",
         "-n", "Key4hep",
         "-u", "https://key4hep.github.io/key4hep-doc/",
-        "-x", ".github/*", ".pre-commit-config.yaml", "README.md", "doc/ReleaseNotes.md", "-f"]
+        "-x", ".github/*", ".pre-commit-config.yaml", "README.md", "doc/ReleaseNotes.md", "*.xml", "-f"]