Opt into dependabot GitHub actions version updates (#2086)

Summary: Opt into dependabot GitHub actions version updates

Earlier today, the download/upload artifacts actions were deprecated and
started failing builds (#2079). There are other actions will be
deprecated soon, so let's opt into dependabots updates to stay ahead of
these notices.

> Your workflow is using a version of actions/cache that is scheduled
for deprecation, actions/cache@88522ab.
Please update your workflow to use either v3 or v4 of actions/cache to
avoid interruptions. Learn more:
https://github.blog/changelog/2024-12-05-notice-of-upcoming-releases-and-breaking-changes-for-github-actions/#actions-cache-v1-v2-and-actions-toolkit-cache-package-closing-down

There are other alternatives (like Renovatebot). I went for this since
it's already in place to get coverage quickly, but open to exploring
other options in the future.

Relevant Issues: N/A

Type of change: /kind cleanup

Test Plan: Read the docs on the setting changed

Signed-off-by: Dom Del Nano <ddelnano@gmail.com>

Author: ddelnano

.github/dependabot.yml

@@ -17,8 +17,7 @@ updates:
   directory: /
   schedule:
     interval: daily
-  # Disable version updates but keep security updates
-  open-pull-requests-limit: 0
+  open-pull-requests-limit: 1
 
 - package-ecosystem: pip
   directory: /bazel/external/ubuntu_packages