lua sandbox: fix syntactic sugar for `cache` table in order for tab-completion to work properly

3 jobs for add_libedit_2 in 1 minute and 37 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed build:linux:amd64 #2546
docker linux amd64

00:00:30

 
  Test
passed deckard:linux:amd64 #2548
docker linux amd64

00:01:06

passed test:linux:amd64 #2547
docker linux amd64

00:00:26