Revert " Switch from Dependabot to update-dependencies (#2042)"

This reverts commit d75d0c4.

Temporarily revert the Python update-dependencies workflow because the
required GitHub App is not yet installed for the opensafely organization
and its credentials are unavailable.
This restores Dependabot Python version updates while the app is being
configured. We can reintroduce the workflow once the required app ID and
key are available.

Author: nishtha-kalra

.github/dependabot.yml

@@ -1,6 +1,28 @@
 version: 2
 
 updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "08:00"
+      timezone: "Europe/London"
+    cooldown:
+      default-days: 7
+    groups:
+      production-dependencies:
+        dependency-type: "production"
+      development-dependencies:
+        dependency-type: "development"
+    allow:
+      - dependency-type: "all"
+    ignore:
+      # mkdocs has a file reload bug with newer click versions,
+      # so pin until this is resolved:
+      # https://github.com/mkdocs/mkdocs/issues/4032
+      - dependency-name: "click"
+
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:

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

@@ -136,6 +136,3 @@ wordcount: build
     #!/usr/bin/env bash
     set -euo pipefail
     find site/ -name '*.html' -exec python scripts/wordcount.py {} + | awk '{sum += $1} END {print "Total words in documentation:", sum}'
-
-# Update prod and dev dependencies
-update-dependencies: (upgrade 'prod') (upgrade 'dev')