docs: minor update in generation_metageneration.rst (missing space)

[jakubczaplicki]

Minor update in generation_metageneration.rst (missing space)

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• [ n/a ] Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• [ n/a ] Ensure the tests and linter pass
• [ n/a ] Code coverage does not decrease (if any source code was changed)
• [ n/a ] Appropriate docs were updated (if necessary)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

For more information, open the CLA check for this pull request.

[jakubczaplicki]

🚀

[cojenco]

Thanks @jakubczaplicki for the patch!