[infra] Remove unused isolates

Some of these use the now-deprecated "command" feature.

Change-Id: I7e0bf0141821e2807146d9b0bb99a69da3a47fd2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/291037
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
5 files changed