Simplify error message body for catalog source connection errors

[Taj010]

Description

The source status error modal suggested checking the organization and retrying, which implies causes (org / access token) the UI does not support and may be wrong. This PR adjusted it to show a single neutral line: “The system cannot establish a connection to the source.” The full backend error string is shown unchanged below it (via existing errorMessage prop from CatalogSourceStatus).

How Has This Been Tested?

Manually: Model Catalog Settings → source in error state → click the failed/error link → confirm the modal shows only the short intro line, then the exact backend error text with no org/credential troubleshooting sentence.

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If you have UI changes

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[Philip-Carneiro]

this change will not be necessary after merge of #2526