bump zoekt

Created by: stefanhengl

• f150b3a ctags: only include log output for debug
• 781cfea merging: tolerate process interruptions during merging
• 881cec1 indexserver: add debug subcommand
• 27375b3 indexserver: remove deprecated GetIndexOptions
• 1210f0f webserver: remove kubernetes sd drain time
• b5c8272 indexserver: remove atomics for fingerprint
• 0316d52 shardedSearcher - implement functionality for filetombstones
• 8082708 all: switch to RFC3339 for timestamps in log files
• 9d43e8e merging: add unit test for explode
• 39b2af4 merging: support exploding compound shards

Test Plan

We deploy Zoekt manually outside the CI. This PR just brings the Sourcegraph repo up to date with what is already deployed.