Make proc-macro2 available to product and vendor am: 1ea12c6feb am: 051ccb49c8

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/proc-macro2/+/2476452

Change-Id: Ib511677667b1318b78f467c40e28d75bafd74ba5
Signed-off-by: Automerger Merge Worker <[email protected]>