#25317 [JAVA][FEIGN] Remove deprecated QueryMap encoded parameter

encoded has been deprecated since Feign 10.7 (Nov 2019) and no longer does anything.

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. (@KannaKim @martin-mfg @lwlee2608 )

---

Summary by cubic

Removes the deprecated encoded attribute from @QueryMap annotations in generated Feign clients. The attribute has been a no-op since Feign 10.7 (Nov 2019), so query parameter handling is unchanged.