Remove "PYTHONHOME" setting from embed-test since it seems to break the I/O...

Remove "PYTHONHOME" setting from embed-test since it seems to break the I/O encoding setup in (at least) Py3.8+ venvs.

Demos/embed/Makefile

@@ -49,5 +49,5 @@ clean:
 	@rm -f *~ *.o *.so core core.* *.c embedded test.output
 
 test: clean all
-	PYTHONHOME=$(PYPREFIX) LD_LIBRARY_PATH=$(LIBDIR1):$$LD_LIBRARY_PATH ./embedded > test.output
+	LD_LIBRARY_PATH=$(LIBDIR1):$$LD_LIBRARY_PATH ./embedded > test.output
 	$(PYTHON) assert_equal.py embedded.output test.output