Update to syn-2 am: 06ea9e5af4 am: 01485df57e am: 12cc499db7 am: f0884fc0c4

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/bindgen/+/2520775

Change-Id: I2accbeacea1b21b2d59c23ee041d41eea7610524
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>