Upgrade to GitHub-native Dependabot

[dependabot-preview]

Dependabot Preview will be shut down on August 3rd, 2021. In order to keep getting Dependabot updates, please merge this PR and migrate to GitHub-native Dependabot before then.

Dependabot has been fully integrated into GitHub, so you no longer have to install and manage a separate app. This pull request migrates your configuration from Dependabot.com to a config file, using the new syntax. When merged, we'll swap out dependabot-preview (me) for a new dependabot app, and you'll be all set!

With this change, you'll now use the Dependabot page in GitHub, rather than the Dependabot dashboard, to monitor your version updates, and you'll configure Dependabot through the new config file rather than a UI.

If you've got any questions or feedback for us, please let us know by creating an issue in the dependabot/dependabot-core repository.

Learn more about migrating to GitHub-native Dependabot

Please note that regular @dependabot commands do not work on this pull request.

[codecov]

Codecov Report

Merging #1632 (ea8f9e3) into master (c1d8b03) will decrease coverage by 1.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1632      +/-   ##
==========================================
- Coverage   68.43%   67.30%   -1.13%     
==========================================
  Files          59       59              
  Lines        3957     3949       -8     
==========================================
- Hits         2708     2658      -50     
- Misses        835      860      +25     
- Partials      414      431      +17     

Impacted Files	Coverage Δ
core/sequencer/server.go	72.56% <0.00%> (-7.99%)	⬇️
core/sequencer/election/tracker.go	69.86% <0.00%> (-6.85%)	⬇️
core/sequencer/trillian_client.go	60.52% <0.00%> (-6.58%)	⬇️
impl/mysql/mutationstorage/mutations.go	65.71% <0.00%> (-5.72%)	⬇️
impl/authorization/authorization.go	72.22% <0.00%> (-4.71%)	⬇️
impl/mysql/directory/storage.go	65.32% <0.00%> (-1.62%)	⬇️
impl/mysql/mutationstorage/mutation_logs.go	69.23% <0.00%> (-1.40%)	⬇️
core/integration/client_tests.go	83.33% <0.00%> (-1.03%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c1d8b03...ea8f9e3. Read the comment docs.

[dependabot-preview]

As a reminder, Dependabot Preview will be shut down on August 3rd, 2021. You can merge this pull request to migrate to GitHub-native Dependabot. You can read the docs to learn more about what's changing, as well as find out how to get support if you need help migrating.