ci(dependabot): update all packages weekly (#173)

This PR changes the configuration of dependabot to update all packages
weekly. I originally wanted to update only LLVM weekly and everything
else daily but I coudln't find out the right way to do this, so I am
giving up. I rather only update all packages weekly than having to
update LLVM every single day.

Signed-off-by: Ingo Müller <[email protected]>

Author: ingomueller-net

.github/dependabot.yml

@@ -1,17 +1,6 @@
 version: 2
 updates:
-  # Special handling for LLVM, to avoid too much noise.
-  - package-ecosystem: "gitsubmodule"
-    directory: "/third_party/"
-    schedule:
-      interval: "weekly"
-    allow:
-      - dependency-name: "llvm-project"
-
-  # All other git submodules.
   - package-ecosystem: "gitsubmodule"
     directory: "/"
     schedule:
-      interval: "daily"
-    ignore:
-      - dependency-name: "third_party/llvm-project"
+      interval: "weekly"