docs: fix typos in msm comments and repr docs

[fifalodm]

This PR fixes minor typos and improves clarity in documentation and comments:

• src/derive/field/common.rs

  • Corrected extra backtick in $field::Repr description.

• src/msm.rs

  • Fixed wording in Booth encoding comment (window + 1`` → window + 1`).
  • Corrected sample indexing array (removed stray backticks).
  • Fixed grammar/typos in comments (skip in on curve check → skip on-curve check, accumumator → accumulator, schedular → scheduler).

Impact

• No functional code changes.
• Improves readability and consistency of documentation.