Drop principal redefinition

It seems to be no longer needed, and requires divergent code for different maxima versions

Author: antonio-rojas

src/sage/interfaces/maxima_lib.py

@@ -164,7 +164,6 @@
 ecl_eval("(initialize-runtime-globals)")
 ecl_eval("(setq $nolabels t))")
 ecl_eval("(defun add-lineinfo (x) x)")
-ecl_eval('(defun principal nil (cond ($noprincipal (diverg)) ((not *pcprntd*) (merror "Divergent Integral"))))')
 ecl_eval("(remprop 'mfactorial 'grind)")  # don't use ! for factorials (#11539)
 ecl_eval("(setf $errormsg nil)")