Update dependabot.yml and remove custom workflow

Since June 25 2024, dependabot has added multi-directory support for
dependencies. As the existing bump-deps.yml was meant as a workaround
for this, we can safely remove it and rely solely on dependabot instead.

Signed-off-by: David Son <davbson@amazon.com>

Author: sondavidb

.github/dependabot.yml

@@ -3,20 +3,7 @@ updates:
 
   # Automatic upgrade for go modules.
   - package-ecosystem: "gomod"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    ignore:
-      # skip grpc because the current latest not compatible with containerd 1.7
-      # skip k8s deps since they use the latest go version/features that may
-      # not be in the go version soci uses
-      # Also ignored in /scripts/bump-deps.sh
-      - dependency-name: "google.golang.org/grpc"
-      - dependency-name: "k8s.io/*"
-
-  # Automatic upgrade for go modules of cmd package.
-  - package-ecosystem: "gomod"
-    directory: "/cmd"
+    directories: ["/", "/cmd"]
     schedule:
       interval: "daily"
     ignore: