Upgrade futures-macro to 0.3.26 am: af43963a44

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-macro/+/2438873

Change-Id: I9511ae64579b80110ceb04eda47800953a574028
Signed-off-by: Automerger Merge Worker <[email protected]>