docs: sync translated MANPAGER examples

[JSap0914]

Summary

• Align the Chinese, Japanese, Korean, and Russian MANPAGER examples with the current English README's bat -plman guidance.
• Remove stale col/awk pre-filtering, MANROFFOPT, and old Mandoc shell-wrapper notes that predate bat's built-in overstrike handling for Manpage/Command Help syntax.
• Correct the Chinese Debian/Ubuntu note so it no longer reverses bat and batcat.

Fixes #3730.

Verification

• gh pr list -R sharkdp/bat --state open --search "3730 doc inconsistency readme manpager language help" --json number,title,url,headRefName,author
• git diff --check
• cargo test --doc
• cargo test --test integration_tests strip_overstrike
• cargo test test_strip_overstrike
• ./target/debug/bat --help --color=never --decorations=never --paging=never | rg -n -- '--language|--strip-ansi|--help'
• printf 'B\bBold _\bunder\n' | ./target/debug/bat --color=always --decorations=never --paging=never --language=man | python3 -c 'import sys; data=sys.stdin.buffer.read(); print("contains_backspace=", b"\\x08" in data); print("contains_Bold=", b"Bold" in data); print("bytes=", data[:80])'
• rg -n 'const MANPAGE_SYNTAX|const COMMAND_HELP_SYNTAX|strip_overstrike|language: if use_color|bat -plman|col -bx|awk|MANROFFOPT|Mandoc' README.md doc/README-zh.md doc/README-ru.md doc/README-ko.md doc/README-ja.md src/bin/bat/app.rs src/printer.rs src/preprocessor.rs tests/integration_tests.rs

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