Drop Cirrus CI due to flakiness (#948)

.cirrus.yml

@@ -1,43 +0,0 @@
-task:
-  name: test [ARM]
-  arm_container:
-    image: rust:1.63.0
-    cpu: 4
-    memory: 8G
-  registry_cache:
-    folder: $CARGO_HOME/registry
-    fingerprint_script: cat Cargo.lock
-  target_cache:
-    folder: target
-    fingerprint_script:
-      - rustc --version
-      - cat Cargo.lock
-  build_script:
-    - apt-get update -qqy
-    - apt-get install -qqy clang
-    - rustup component add clippy rustfmt
-    - cargo check --all --locked
-    - cargo build --all --locked
-  test_script:
-    - cargo test --all --locked
-    - cargo clippy -- -D warnings
-    - cargo fmt --all -- --check
-  before_cache_script: rm -rf $CARGO_HOME/registry/index
-
-
-task:
-  compute_engine_instance:
-    image_project: cirrus-images
-    image: family/docker-builder-arm64
-    architecture: arm64
-    platform: linux
-    cpu: 2
-    memory: 4G
-
-  name: integration [ARM]
-  env:
-    CIRRUS_ARCH: arm64
-  build_script:
-    - docker build --build-arg=ARCH=aarch64 -f Dockerfile.ci . --rm -t electrs:tests
-  test_script:
-    - docker run -v $PWD/contrib/:/contrib -v $PWD/tests/:/tests --rm electrs:tests bash /tests/run.sh