Add tomli to openenv real doc-build deps (#803)

openenv.cli.importers falls back to `import tomli as tomllib` on
Python < 3.11, which is what the shared workflow runners use.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: mishig25

src/doc_builder/mock_deps/openenv.txt

@@ -11,3 +11,4 @@ real:requests
 real:pydantic
 real:aiohttp
 real:typer
+real:tomli  # py<3.11 fallback for tomllib in openenv.cli.importers