Remove SafeStack jobs

This was added in https://review.skia.org/62743; broke in
https://review.skia.org/1248516 (a runtime error
`/b/s/w/ir/build/dm: symbol lookup error: /b/s/w/ir/build/dm: undefined symbol: _ZNSt3__113__hash_memoryEPKvm`

and I don't remember this catching anything not caught by ASAN. Let's
get rid of it.

Change-Id: Ib12a9f1ff93d9726e86d60068137b5b55f677ae1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1253097
Auto-Submit: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
Commit-Queue: Nicolette Prevost <nicolettep@google.com>