Fix cljfmt options serialization for format-code

[kovan]

Fixes #3209.

Summary

cider--nrepl-format-code-request-options was dropping non-map cljfmt options.
As a result, options like remove-consecutive-blank-lines? and
remove-multiple-non-indenting-spaces? never reached the format-code nREPL op.

This change preserves all options, while keeping special nREPL-dict encoding for
nested map options like indents and alias-map.

Checks done

1. Reproduced on pre-fix code (75dc57ae):

   • Evaluating formatter option serialization with
     (("remove-consecutive-blank-lines?" t) ("remove-multiple-non-indenting-spaces?" t))
   • Result: (nil nil (dict))

2. Applied the fix and re-ran the same evaluation:

   • Result: (t t (dict "remove-consecutive-blank-lines?" t "remove-multiple-non-indenting-spaces?" t))

3. Ran focused tests after the fix:

   • eldev -dtT -p test test --file test/cider-client-tests.el .
   • Result: Ran 17 specs, 0 failed

[bbatsov]

The changes look good. Don't forget to reflect them in the changelog.

[kovan]

Done, added a changelog entry. Thanks!