Remove 1s sleep between each package in the A/B OTA postinstall dexopt process.

This sleep makes OTA dexopt runs take significantly longer, but even so
it's not sufficient to avoid jank (cf. b/237017087).

If this process takes too much resources then it can be tuned through
the `OtaProfiles` task profile, `dalvik.vm.background-dex2oat-cpu-set`
and/or `dalvik.vm.background-dex2oat-threads`. It's also possible to
cut down the work done before the OTA reboot with `MAXIMUM_PACKAGES`.

Test: Manual OTA update
Bug: 199756868
Bug: 237017087
Change-Id: Id2b460a99da19d42238d3aa0165c1792fe303398