[stable-2.18] dnf tests: unique environment/group name (#84785) (#84786)

Prevents `Group state for \"customenvgroup\" not found` error which may
or may not be a regression in dnf5. Just name groups/envs uniquely to
workaround the issue.
(cherry picked from commit 09391f38f0)

test/integration/targets/setup_rpm_repo/files/comps.xml

@@ -14,7 +14,7 @@
 
   <group>
     <id>customenvgroup</id>
-    <name>Custom Environment Group</name>
+    <name>Custom Group in Environment</name>
     <description></description>
     <default>false</default>
     <uservisible>false</uservisible>