Install uv on GHA runner

We recently moved dependency management over to uv
locally and in CI. Most of our workflows do not
use uv in CI, and only require uv for processes
that run inside docker containers where uv is
installed.

However, our update-dependencies workflow runs a
'bump-cutoff' recipe. This recipe first tries to
execute uvx but becasue uv isn't installed on the
runner, the workflow fails.

This commit adds the uv install we need on the
runner for this workflow.

Author: KatieB5

.github/workflows/update-python-dependencies.yml

@@ -23,6 +23,7 @@ jobs:
     - uses: opensafely-core/setup-action@5b3030fbbcf069c94e352b4f0a94100fae4dbd82 # v1.6.1
       with:
         install-just: true
+        install-uv: true
 
     - uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
       id: generate-token