Whitelisting file Index.xml from rpminspect xml check

Reason is, that the bug is already reported on upstream:
https://jira.mariadb.org/browse/MDEV-26905.
Also we currently do not know how to fix it. If we eventually figure out
how to fix this bug, then the patch would be submitted directly to the
upstream, rather than to downstream, to avoid unintentionally breaking
some code that relied on the malformed XML.

rpminspect.yaml

@@ -2,8 +2,8 @@
 # are the invalid xmls (except for Index.xml) present in the sources on purpose
 # and they can be removed from xmllint rpminspect check in the CI process.
 #
-# A bug report [https://jira.mariadb.org/browse/MDEV-26905] was created for the
-# Index.xml file.
+# A bug report [https://jira.mariadb.org/browse/MDEV-26905] was created in the upstream
+# for the Index.xml file.
 #
 # Fedora CI picks up the rpmlimspect.yaml for specific package in the dist-git repo
 #[ref: https://rpminspect.readthedocs.io/en/latest/configuration.html#rpminspect-yaml]
@@ -15,6 +15,7 @@ xml:
     - /usr/share/mysql-test/std_data/ldml/Index.xml
     - /usr/share/mysql-test/plugin/sphinx/sphinx/testdata.xml
     - /usr/share/mysql-test/plugin/connect/connect/std_data/nocs.xml
+    - /usr/share/mariadb/charsets/Index.xml
 
 # ignore bad functions in resolveip binary, based on BZ1973194
 # all forbidden functions listed in main rpminspect config