docs: mirroring support in Traefik is not implemented yet

[kostis-codefresh]

Clarifies #2890

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
No Duplication information

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (20e00e4) 81.68% compared to head (7264c5a) 81.68%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2904   +/-   ##
=======================================
  Coverage   81.68%   81.68%           
=======================================
  Files         133      133           
  Lines       20309    20309           
=======================================
  Hits        16589    16589           
  Misses       2862     2862           
  Partials      858      858           

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[github-actions]

Go Published Test Results

2 030 tests   2 030 ✔️  2m 39s ⏱️
   118 suites         0 💤
       1 files           0 ❌

Results for commit 7264c5a.

[github-actions]

E2E Tests Published Test Results

    4 files      4 suites   3h 38m 1s ⏱️
102 tests   88 ✔️   6 💤 8 ❌
418 runs  385 ✔️ 24 💤 9 ❌

For more details on these failures, see this check.

Results for commit 7264c5a.