Instruct rpminspect to ignore xml jinja templates (teemtee#4635)

The `_base.xml.j2` template is incorrectly detected as `xml` and then
always reported as a problem when releasing a new `tmt` in Fedora. Let's
get rid of the false warning.

* rpminspect/rpminspect#1545

Author: psss

packaging/rpm/rpminspect.yaml

@@ -3,3 +3,8 @@ addedfiles:
   ignore:
     # rpminspect forbids /var/tmp prefix by default
     - /var/tmp/tmt
+xml:
+  ignore:
+    # rpminspect is unable to detect jinja templates
+    # https://github.com/rpminspect/rpminspect/issues/1545
+    - /usr/lib/python3*/site-packages/tmt/steps/report/junit/templates/*.xml.j2