update links in integrations.rst (#1418)
A number of the links in integrations.rst don't seem to lead to the
intended section in the unstructured documentation.
For example:
```See the `stage_for_weaviate <https://unstructured-io.github.io/unstructured/bricks.html#stage-for-weaviate>`_ docs for details```
It seems this link should direct to here instead: https://unstructured-io.github.io/unstructured/bricks/staging.html#stage-for-weaviate
