Adjust BWC versions for API key auth test.

ywangd · ywangd · commit edf27cd765cc · 2020-07-14T00:38:42.000+10:00
API key realm name is not available in authentication metadata prior to v7.5. The issue is tracked at #59425
diff --git a/x-pack/qa/rolling-upgrade/src/test/resources/rest-api-spec/test/mixed_cluster/120_api_key_auth.yml b/x-pack/qa/rolling-upgrade/src/test/resources/rest-api-spec/test/mixed_cluster/120_api_key_auth.yml
@@ -3,6 +3,8 @@
 
   - skip:
       features: headers
+      version: " 7.5.0 - "
+      reason: "API key realm name is in metadata since v7.5. https://github.com/elastic/elasticsearch/issues/59425"
 
   - do:
       security.create_api_key:
