lang/spidermonkey52: fix build with GCC-based architectures

With gcc9, build fails:
/usr/local/poudriere/ports/default/lang/spidermonkey52/work/firefox-52.9.0esr/js/src/jsapi-tests/testPrintf.cpp: In member function 'virtual bool cls_testPrintf::run(JS::HandleObject
)':
/usr/local/poudriere/ports/default/lang/spidermonkey52/work/firefox-52.9.0esr/js/src/jsapi-tests/testPrintf.cpp:58:20: error: '%s' directive argument is null [-Werror=format-overflow

]

58 |     CHECK(print_one("(null)", "%s", zero()));

Remove the test printf:
CHECK(print_one("(null)", "%s", zero()));
to fix build.

PR: 239507
Approved by: tcberner (mentor), portmgr blanket
Differential Revision: https://reviews.freebsd.org/D21144