fix to build with boxed-cpp

[topazus]

Description

The PR is related to contour-terminal/boxed-cpp#9

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[topazus]

The error appeared in Ubuntu 20.04 was seemingly caused by the reason that GCC 9 does not support C++ 20 concepts.

[Yaraslaut]

The error appeared in Ubuntu 20.04 was seemingly caused by the reason that GCC 9 does not support C++ 20 concepts.

I see that g++10 is there https://packages.ubuntu.com/focal/g++-10
We can update GitHub action to compile with gcc-10

[Yaraslaut]

@topazus Can you update github action then please? If you are bussy i can do it as well

[topazus]

I do not have a compuer at hand right now. Grateful if you do this. @Yaraslaut

[Yaraslaut]

@topazus I updated PR, builds are fine now, if you fill that PR is no longer in draft, make it then ready for review to proceeed with merging

[christianparpart]

I just have a minor improvement suggestion. Otherwise, many thanks!