test: disable Python 3.13 CI xapian build. Fails with compile error. ... libtool: compile: g++ -DHAVE_CONFIG_H -I. -I.. -I/opt/hostedtoolcache/Python/3.13.0-alpha.6/x64/include/python3.13 -fno-strict-aliasing -Wall -Wno-unused -Wno-uninitialized -fvisibility=hidden -g -O2 -MT xapian_wrap.lo -MD -MP -MF .deps/xapian_wrap.Tpo -c xapian_wrap.cc -fPIC -DPIC -o .libs/xapian_wrap.o xapian_wrap.cc: In constructor ‘XapianSWIG_Python_Thread_Block::XapianSWIG_Python_Thread_Block()’: xapian_wrap.cc:87:13: error: ‘PyEval_ThreadsInitialized’ was not declared in this scope 87 | if (PyEval_ThreadsInitialized()) { | ^~~~~~~~~~~~~~~~~~~~~~~~~ xapian_wrap.cc: In constructor ‘XapianSWIG_Python_Thread_Allow::XapianSWIG_Python_Thread_Allow()’: xapian_wrap.cc:109:47: error: ‘PyEval_ThreadsInitialized’ was not declared in this scope 109 | XapianSWIG_Python_Thread_Allow() : status(PyEval_ThreadsInitialized()) { | ^~~~~~~~~~~~~~~~~~~~~~~~~ make[3]: *** [Makefile:782: xapian_wrap.lo] Error 1