remove case sensitive for libcapsimg path

[zognic]

By default, Amiberry looks inside "Amiberry/plugins"
even with AMIBERRY_HOME_DIR=~/amiberry set in lower case

Could you please remove the hard path with A in uppercase

	// 3: Check for ~/Amiberry/plugins
	const auto user_home_dir = getenv("HOME");
	if (user_home_dir != nullptr)
	{
		if (!directory_exists(user_home_dir, "/Amiberry"))
		{
			my_mkdir((std::string(user_home_dir) + "/Amiberry").c_str());
		}
		// $HOME/Amiberry exists, use it
		if (!directory_exists(user_home_dir, "/Amiberry/plugins"))
		{
			my_mkdir((std::string(user_home_dir) + "/Amiberry/plugins").c_str());
		}
		write_log("Using plugins directory from $HOME/Amiberry/plugins\n");
		return { std::string(user_home_dir) + "/Amiberry/plugins" };
	}