Update URL for moved repositories

Strictly speaking, the links weren't broken.

However, there's a really weird intersection of GitHub and lychee's behaviour
here.

Two behavioural points to explain.

First, GitHub seems to tend to give different response behaviour for
repository redirects, depending on whether the client is a full web
browser or not (my best guess; typically requests to these kinds of
redirects give a 404 via `wget` and `curl`, but maybe sometimes not?).
This behaviour may have changed recently, unless these repositories have
been renamed recently (and I don't believe that to be true).

Second, lychee is one of these clients affected by this behaviour.

So what happens when the link check fails:

1. The lychee action runs and lychee checks a repository URL that is
   going to get redirected.
1. GitHub's servers now give a 404 for that URL-to-be-redirected.
1. lychee notes down in the raw logs that the URL included in the
   documentation source is a 404.
1. The GitHub Actions summary of the action run gives a Markdown
   formatted output.
1. That output has the repository redirect URL updated to the new URL
   for the redirection in the formatted output, magically by GitHub.
   **The new URL never appeared in the logs at all!**
1. **The link works in browser in any case**, partly because this is the
   new URL, and it would even for the original non-redirected URL,
   because these still work in browser. So it's very confusing that it's
   labelled as `404`.

docs/install-docker.md

@@ -40,7 +40,7 @@ To install Docker Desktop on Windows Home [follow these installation instruction
 
    You may be asked to enable the Hyper-V and Containers features, which you should do.
    You can do this by [following these instructions](https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/quick-start/enable-hyper-v).
-   At least one user has had the box ticked on the screen but had to untick and tick again to get this to enable correctly (Detailed in [this issue](https://github.com/ebmdatalab/custom-docker/issues/4)).
+   At least one user has had the box ticked on the screen but had to untick and tick again to get this to enable correctly (Detailed in [this issue](https://github.com/ebmdatalab/notebook-template/issues/4)).
 
 1. Starting Docker can take a while — up to 5 minutes. While it's doing
    so, an animation runs in the notification area:<br>

docs/legacy/study-def-expectations.md

@@ -13,7 +13,7 @@ You can also [provide your own dummy data](#providing-your-own-dummy-data).
 ## Defining `return_expectations`
 
 Every variable in a study definition must have a `return_expectations` argument defined (with the exception of the `population` variable).
-This defines the general shape or distribution of the variables in the dummy data used for developing the code.  It is currently relatively unsophisticated; each variable is generated independently of all others. In most cases, dummy data is good enough to test that it is possible to run your study from start to finish, but sometimes not. You can find (and contribute to!) discussions on improving the [dummy data framework](https://github.com/opensafely/cohort-extractor/issues/221).
+This defines the general shape or distribution of the variables in the dummy data used for developing the code.  It is currently relatively unsophisticated; each variable is generated independently of all others. In most cases, dummy data is good enough to test that it is possible to run your study from start to finish, but sometimes not. You can find (and contribute to!) discussions on improving the [dummy data framework](https://github.com/opensafely-core/cohort-extractor/issues/221).
 
 ### Specifying default distributions