github/workflows: remove fuzzing workflow.

[ivanvc]

This job is already running in the Prow infrastructure.

After merging kubernetes/test-infra#34335 it will be blocking, so we can remove this workflow.

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.83%. Comparing base (14cf669) to head (c733872).
Report is 2 commits behind head on main.

Additional details and impacted files

see 18 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #19422      +/-   ##
==========================================
- Coverage   68.95%   68.83%   -0.13%     
==========================================
  Files         420      420              
  Lines       35753    35753              
==========================================
- Hits        24655    24611      -44     
- Misses       9677     9710      +33     
- Partials     1421     1432      +11     

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 14cf669...c733872. Read the comment docs.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr, ivanvc, serathius

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• .github/OWNERS [ahrtr,ivanvc,serathius]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment