Revert^2 "Upgrade spki to 0.7.3" am: 81a66df692

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/spki/+/2881111

Change-Id: Ic1acf52c24753d6dac00bc2dcc6cf489cf01583b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>