Pin watchfiles dependency in documentation for rust compatibility

Fixes

Fixes #5146 by @AetherUnbound

Description

This PR pins the watchfiles dependency, which seems like it's necessary for rust compatibility on install. I also added a comment for the API's dependencies which were modified in #5095, since that library isn't used directly in testing and can be unpinned once the dependency issues are resolved upstream.

Testing Instructions

Run ov just documentation/install and observe that it no longer fails!

Checklist

[x] My pull request has a descriptive title (not a vague title likeUpdate index.md).
[x] My pull request targets the default branch of the repository (main) or a parent feature branch.
[x] My commit messages follow [best practices][best_practices].
[x] My code follows the established code style of the repository.
[ ] I added or updated tests for the changes I made (if applicable).
[x] I added or updated documentation (if applicable).
[x] I tried running the project locally and verified that there are no visible errors.
[ ] I ran the DAG documentation generator (ov just catalog/generate-docs for catalog PRs) or the media properties generator (ov just catalog/generate-docs media-props for the catalog or ov just api/generate-docs for the API) where applicable.

[best_practices]: https://git-scm.com/book/en/v2/Distributed-Git-Contributing-to-a-Project#_commit_guidelines

Developer Certificate of Origin

``` Developer Certificate of Origin Version 1.1 Copyright (C) 2004, 2006 The Linux Foundation and its contributors. 1 Letterman Drive Suite D4700 San Francisco, CA, 94129 Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Developer's Certificate of Origin 1.1 By making a contribution to this project, I certify that: (a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or (b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or (c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it. (d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved. ```

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