docs: avoid backlinks from the issue template example

[alexaka1]

Use redirect.github.com for the fixed sponsorship example in the bug-report template. GitHub documents this hostname as the way to keep links navigable without adding backlinks to the referenced issue, so unrelated bug reports no longer populate the example issue's timeline.

The current PR template and the other issue templates contain no equivalent example links requiring a change.

Fixes #25207

Validation: git diff --check passed; the redirect URL returned HTTP 301 to the original example issue. Build and sample regeneration are not applicable to this Markdown-only change. This PR is not language-specific.

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

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Summary by cubic

Updates the bug-report template to link the sponsorship example through redirect.github.com, so unrelated bug reports no longer add backlinks to the example issue's timeline. Fixes #25207.

^{Written for commit a55fd03. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{View guided diff | Re-trigger cubic}