docs: use a placeholder project id in the captured error message

The 403 fixture in test_errors.py was copied verbatim from a live API
response, so it carried the real project id of the account used for
verification. deferred.md named the same project. Neither is a secret,
but this repository is about to be public and there is no reason to
publish the id.

The classifier matches on the phrases "has not been used in project" and
"it is disabled" (errors.py:122-123), never on the id, so substituting
it changes nothing: the full suite passes unchanged. What the comment
records — that this message was observed verbatim from a live 403 on
2026-09-01 — survives, because the sentence structure is what makes it
evidence.

Author: hypn4

specs/001-gcp-support-mcp/deferred.md

@@ -14,7 +14,7 @@ without reading the conversation that produced them.
 
 ## The one blocker behind two of them
 
-`projects/kktae-demo` — the project used for live verification — **has no paid
+`projects/my-project` — the project used for live verification — **has no paid
 support plan.** Reading works; creating a case does not:
 
 ```

tests/unit/test_errors.py

@@ -15,9 +15,9 @@
 PERM_403 = "Permission 'cloudsupport.cases.list' denied on resource."
 # Observed verbatim from a live 403 on 2026-09-01.
 DISABLED_403 = (
-    "Google Cloud Support API has not been used in project kktae-demo before or it is "
+    "Google Cloud Support API has not been used in project my-project before or it is "
     "disabled. Enable it by visiting https://console.developers.google.com/apis/api/"
-    "cloudsupport.googleapis.com/overview?project=kktae-demo then retry."
+    "cloudsupport.googleapis.com/overview?project=my-project then retry."
 )