Unbreak build with boost 1.73 by removing obsoleted boost patch.

Spotted by aja@ merci!

cad/openscad/patches/patch-src_import_cc

@@ -1,15 +0,0 @@
-$OpenBSD: patch-src_import_cc,v 1.1 2020/12/13 20:40:55 sthen Exp $
-
-Fix build with newer Boost.
-
-Index: src/import.cc
---- src/import.cc.orig
-+++ src/import.cc
-@@ -50,7 +50,6 @@ namespace fs = boost::filesystem;
- #include <boost/assign/std/vector.hpp>
- using namespace boost::assign; // bring 'operator+=()' into scope
- 
--#include <boost/detail/endian.hpp>
- #include <cstdint>
- 
- extern PolySet * import_amf(std::string, const Location &loc);