Ignore invalid vndk snapshot versions

Device targets may set PRODUCT_EXTRA_VNDK_VERSIONS to include invalid
snapshot versions with the trunk-stable next configuration.
Ignore those versions that are less than or equal to the
PLATFORM_VNDK_VERSION.

Bug: 296488609
Test: lunch cf_x86_64_phone-next-userdebug; m nothing
Change-Id: I2ba9d7f41a0d75db034b1c08d15f2796ef9ed506