Dependabot: Group all CI dependencies (#5145)

Dependabot is going a bit crazy lately and spamming up a lot of merge
requests. Going to group all the CI deps into one and reducing the
frequency to weekly.
Maybe we can do some more aggressive batching for the Rust deps as well.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

.github/dependabot.yml

@@ -5,13 +5,17 @@ updates:
     directory: '/'
     labels: ["A1-insubstantial", "R0-silent"]
     schedule:
-      interval: daily
+      interval: weekly
+    groups:
+      ci_dependencies:
+        patterns:
+        - "*"
   # Update Rust dependencies:
   - package-ecosystem: "cargo"
     directory: "/"
     labels: ["A1-insubstantial", "R0-silent"]
     schedule:
-      interval: "daily"
+      interval: "weekly"
     groups:
       # We assume these crates to be semver abiding and can therefore group them together.
       known_good_semver: