make: numerically compare the major version of pandoc to be greater then or equal to 2

[t-nil]

IMPORTANT: PRs without the template will be CLOSED

Fix man page being built without smart-markdown, because pandoc versions greater 2 are not detected properly

The makefile had a hardcoded major version check of pandoc against 2. In my pandoc 3 installation the check failed and smart-markdown was not used, even though it is available. That caused double dashes to be rendered as single, long dashes.

This fix causes make to numerically compare the major version to be greater then or equal to 2.

Fixes #7046

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[pukkandan]

Have you tested the resulting file with pandoc 3 is correct? You can try diffing with pandoc 2 result.

[t-nil]

Have you tested the resulting file with pandoc 3 is correct? You can try diffing with pandoc 2 result.

> pandoc -v
pandoc 3.1.2
Features: +server +lua
Scripting engine: Lua 5.4
User data directory: /home/ra1n/.local/share/pandoc
Copyright (C) 2006-2023 John MacFarlane. Web:  https://pandoc.org
This is free software; see the source for copying conditions. There is no
warranty, not even for merchantability or fitness for a particular purpose.
> pandoc2 -v
pandoc2 2.19.2
Compiled with pandoc-types 1.22.2.1, texmath 0.12.5.2, skylighting 0.13,
citeproc 0.8.0.1, ipynb 0.2, hslua 2.2.1
Scripting engine: Lua 5.4
User data directory: /home/ra1n/.local/share/pandoc
Copyright (C) 2006-2022 John MacFarlane. Web:  https://pandoc.org
This is free software; see the source for copying conditions. There is no
warranty, not even for merchantability or fitness for a particular purpose.

pandoc -s -f markdown-smart -t man yt-dlp.1.temp.md -o yt-dlp.1
pandoc2 -s -f markdown-smart -t man yt-dlp.1.temp.md -o yt-dlp.1_pandoc2
diff yt-dlp.1*

With the commands displayed above, the diff is empty on my side. I think the change can be pushed.

[elig0n]

@pukkandan Why has this not been merged until now ?