CI: Disable git submodule updates with dependabot

Disabled because dependabot needs access to GHA secrets and the
submodule updates aren't super critical right now

The GitHub Actions are still left enabled because they're more important
to keep updated, even if it means manually recreating the dependabot PR

Author: ekilmer

.github/dependabot.yml

@@ -8,10 +8,9 @@ updates:
       interval: "daily"
 
   # Maintain dependencies for GitHub Actions
-  - package-ecosystem: "gitsubmodule"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    ignore:
-      # McSema has a pinned version of anvill
-      - dependency-name: "anvill-mcsema"
+  # NOTE(ekilmer): Disabled because dependabot needs access to GHA secrets and
+  # the submodule updates aren't super critical right now
+  # - package-ecosystem: "gitsubmodule"
+  #   directory: "/"
+  #   schedule:
+  #     interval: "weekly"