"Error loading artifact" messages related to adobe-internal artifacts/bundles

since version 1.6.20, AEM analyzer maven plugin reports tons of error message on each run about missing artifacts. all of them seem to relate to adobe-internal bundles not available in Maven central. this should not be displayed as error, as people outside adobe cannot do anything about it.

this problem was not present in version 1.6.18.

example:
```
[ERROR] Error loading artifact com.adobe.aem:com.adobe.aem.sites-cf-delivery-api:0.0.10 : Unable to get artifact for com.adobe.aem:com.adobe.aem.sites-cf-delivery-api:0.0.10
[ERROR] Error loading artifact com.adobe.aem:graphiql.core:0.0.30 : Unable to get artifact for com.adobe.aem:graphiql.core:0.0.30
[ERROR] Error loading artifact com.adobe.cq.dam:cq-dam-cfm-graphql:0.0.386 : Unable to get artifact for com.adobe.cq.dam:cq-dam-cfm-graphql:0.0.386
[ERROR] Error loading artifact com.adobe.aem:sites-headless:1.2.216-SITES-39116-B0001 : Unable to get artifact for com.adobe.aem:sites-headless:1.2.216-SITES-39116-B0001
[ERROR] Error loading artifact com.adobe.aem:sites-graphql-headless:1.0.56 : Unable to get artifact for com.adobe.aem:sites-graphql-headless:1.0.56
[ERROR] Error loading artifact com.adobe.aem:com.adobe.aem.graphql.sites-base:0.0.152 : Unable to get artifact for com.adobe.aem:com.adobe.aem.graphql.sites-base:0.0.152
[ERROR] Error loading artifact com.adobe.aem:com.adobe.aem.graphql.sling-adapter:0.1.64 : Unable to get artifact for com.adobe.aem:com.adobe.aem.graphql.sling-adapter:0.1.64
[ERROR] Error loading artifact org.apache.sling:org.apache.sling.graphql.core:0.0.37-T20260423092425-d4f779c : Unable to get artifact for org.apache.sling:org.apache.sling.graphql.core:0.0.37-T20260423092425-d4f779c
...
```
Longer list: [error-messages.txt](https://github.com/user-attachments/files/28704089/error-messages.txt)

Reproduce the artifact-loading output with the AEM Analyzer Maven plugin, comparing versions 1.6.18 and 1.6.20 and reviewing the supplied error-messages.txt list. Trace where missing Adobe-internal artifacts are reported; done means unavailable external artifacts no longer produce misleading error messages while relevant failures remain visible.

Written by the indexing model from the issue text.