Disable cross build/tests on Android

Cross is currently broken on Android, see cross-rs/cross#1222

The bug is fixed on master, but a new release of cross hasn't come out
yet.

Signed-off-by: Joe Richey <joerichey@google.com>

.github/workflows/tests.yml

@@ -134,7 +134,9 @@ jobs:
       matrix:
         target: [
           aarch64-unknown-linux-gnu,
-          aarch64-linux-android,
+          # TODO: add Android tests back when the cross cuts a new release.
+          # See: https://github.com/cross-rs/cross/issues/1222
+          # aarch64-linux-android,
           mips-unknown-linux-gnu,
           wasm32-unknown-emscripten,
         ]