chore: Rename docs/rollback.md to docs/features/rollback.md

[alexef]

fixing 404 https://argoproj.github.io/argo-rollouts/features/rollback.md - put it in the expected location

see: https://github.com/argoproj/argo-rollouts/blob/master/mkdocs.yml#L40

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[github-actions]

Go Published Test Results

1 800 tests   1 800 ✔️  2m 30s ⏱️
   102 suites         0 💤
       1 files           0 ❌

Results for commit 85334ca.

[codecov]

Codecov Report

Base: 81.58% // Head: 81.58% // No change to project coverage 👍

Coverage data is based on head (85334ca) compared to base (c3e305d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2438   +/-   ##
=======================================
  Coverage   81.58%   81.58%           
=======================================
  Files         124      124           
  Lines       18959    18959           
=======================================
  Hits        15467    15467           
  Misses       2702     2702           
  Partials      790      790           

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[github-actions]

E2E Tests Published Test Results

    2 files      2 suites   1h 47m 58s ⏱️
  92 tests   79 ✔️ 3 💤 10 ❌
194 runs  178 ✔️ 6 💤 10 ❌

For more details on these failures, see this check.

Results for commit 85334ca.