test: Pin mcp<2 for fastmcp<0.3

scripts/populate_tox/config.py

@@ -312,6 +312,9 @@
         "package": "fastmcp",
         "deps": {
             "*": ["pytest-asyncio", "httpx"],
+            "<0.3.0": [
+                "mcp<2"
+            ],  # Pin added to package in https://github.com/PrefectHQ/fastmcp/commit/5f58621f8b7c7ba257c9837333b09b391f868456#diff-50c86b7ed8ac2cf95bd48334961bf0530cdc77b5a56f852c5c61b89d735fd711
         },
     },
     "openai-base": {