help text: std types should be renamed

[mr-c]

std::string → string
std::filesystem::path → path

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Relevant code: https://github.com/seqan/sharg-parser/blob/main/include/sharg/detail/format_base.hpp#L69-L72

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Core Meeting 24/10/2022

• Make get_type_name_as_string customizable for any type, e.g. strong types.
• Change std::string and std::filesystem::path.
• Rethink other type name strings.

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Partially done for synopsis in #296