Fix duplicate mb_get_info spine entries (7965→7962 count sync)

[PurHur]

Summary

• Remove three duplicate require_once lines in compiler_lib_spine_smoke/main.php for mb_get_info lowering files (JitMbGetInfo, MbGetInfoJitHelper, MbGetInfoRuntime) introduced when Stdlib: mb_get_info()/mb_output_handler() missing — undefined vs Zend mbstring (ext/mbstring/mbstring.c) #20014 landed.
• Restores spine count sync 7962/7962 (was 7965/7962 with duplicate-entry failures in check-selfhost-spine-count-sync).

Test plan

./script/aot-smoke.sh
# aot-smoke: 8 passed, 0 failed

./script/docker-exec.sh -- bash -lc 'php script/check-selfhost-spine-count-sync.php && php script/check-selfhost-spine-coverage-sync.php'
# check-selfhost-spine-count-sync: OK (spine 7962/7962)
# check-selfhost-spine-coverage-sync: OK

./script/phpunit.sh --filter MbGetInfoRuntimeAotTest
# OK (2 tests, 16 assertions)

Related: #20014 (mb_get_info stdlib), spine-sync pattern from #35565 (dom dedup).

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