Remove Android 14 Desktop system image and AVDs

Since Android 15 Desktop builder is up and green, no need to keep 14.

Bug: 394947094
Change-Id: Ic4d29d7ff323f6040bd950e43f40af22f436c47f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6245814
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/main@{#1418301}
NOKEYCHECK=True
GitOrigin-RevId: 291441a974437e8c4d1fb9113b7adaee6f88cfc8