tests: rename 'prj-grp' placeholder to 'my-project' for vendor-agnostic OSS

The dashed identifier is what the test exercises (backticks required for
dashed BQ project IDs); the literal string can be any synthetic value.
'prj-grp' is too close to a real customer-prefix pattern that the OSS
vendor-scrub regex flags. 'my-project' matches placeholders used elsewhere
in the project.

tests/test_admin_validator_backtick_relaxed_for_materialized.py

@@ -13,9 +13,9 @@ def test_materialized_accepts_backticks():
         name="b1",
         source_type="bigquery",
         query_mode="materialized",
-        source_query="SELECT * FROM `prj-grp.ds.tbl`",
+        source_query="SELECT * FROM `my-project.ds.tbl`",
     )
-    assert req.source_query == "SELECT * FROM `prj-grp.ds.tbl`"
+    assert req.source_query == "SELECT * FROM `my-project.ds.tbl`"
 
 
 def test_remote_rejects_backticks():

tests/test_api_admin_materialized.py

@@ -303,14 +303,14 @@ def test_register_materialized_accepts_backtick_source_query(seeded_app, bq_inst
         "/api/admin/register-table",
         json=_materialized_payload(
             name="bt_native",
-            source_query="SELECT * FROM `prj-grp.ds.product_inventory`",
+            source_query="SELECT * FROM `my-project.ds.product_inventory`",
         ),
         headers=_auth(token),
     )
     assert r.status_code in (200, 201, 202), r.json()
     reg = c.get("/api/admin/registry", headers=_auth(token)).json()
     row = next(t for t in reg["tables"] if t["id"] == "bt_native")
-    assert row["source_query"] == "SELECT * FROM `prj-grp.ds.product_inventory`"
+    assert row["source_query"] == "SELECT * FROM `my-project.ds.product_inventory`"
 
 
 def test_update_materialized_accepts_backtick_source_query(