Make duplicate intern string check be debug only

This check was expensive and costing up to 300ms per dex2oat
invocation. Disabling the check reduces OTA/first boot time by
~10-20s for low preopt devices.

Test: test-art-host
Bug: 70934104
Change-Id: I7ed0a0d098bc725c6fbb24318b73816506c2deec