od: remove unused properties from InputDecoder

[cakebaker]

This PR is a follow-up to #14006 and removes the properties used_normal_length and used_peek_length from InputDecoder as they are unused.

[xtqqczze]

does it make sense to use .map now?

[cakebaker]

Good point, thanks! I changed it to use map and added @Devel08 as a co-author.

[codspeed-hq]

Merging this PR will not alter performance

✅ 258 untouched benchmarks
⏩ 149 skipped benchmarks¹

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_{Comparing cakebaker:od_remove_properties (0da745e) with main (b2a617e)²}

Footnotes

1. 149 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (e275cd5) during the generation of this report, so b2a617e was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩