ci: remove Travis CI integration

we are now using Cirrus CI

.travis.yml

@@ -1,117 +0,0 @@
-dist: bionic
-language: python
-python:
-    - 3.6
-    - 3.7
-    - 3.8
-git:
-  depth: false
-before_install:
-  - git tag
-install:
-  - sudo apt-get -y install libsecp256k1-0
-  - pip install -r contrib/requirements/requirements-travis.txt
-cache:
-  - pip: true
-  - directories:
-    - /tmp/electrum-build
-script:
-    - tox
-after_success:
-    - if [ "$TRAVIS_BRANCH" = "master" ]; then pip install requests && contrib/push_locale; fi
-    - coveralls
-jobs:
-  include:
-    - name: "Regtest functional tests"
-      language: python
-      python: 3.7
-      install:
-        - sudo add-apt-repository -y ppa:luke-jr/bitcoincore
-        - sudo apt-get -qq update
-        - sudo apt-get install -yq bitcoind
-        - sudo apt-get -y install libsecp256k1-0
-        - pip install .[tests]
-        - pip install electrumx
-      before_script:
-          - electrum/tests/regtest/start_bitcoind.sh
-          - electrum/tests/regtest/start_electrumx.sh
-      script:
-        - python -m unittest electrum/tests/regtest.py
-      after_success: True
-    - name: "Flake8 linter tests"
-      language: python
-      install: pip install flake8
-      script: flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
-    - stage: binary builds
-      if: (branch = master) OR (tag IS present)
-      name: "Windows build"
-      language: c
-      python: false
-      env:
-        - TARGET_OS=Windows
-      services:
-        - docker
-      before_install:  # we need a newer version of docker; 20.10+ seems to work
-        - sudo rm -rf /var/lib/apt/lists/*
-        - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
-        - sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
-        - sudo apt-get update
-        - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
-        - docker version
-      script:
-        - ELECBUILD_COMMIT=HEAD ./contrib/build-wine/build.sh
-      after_success: true
-    - if: (branch = master) OR (tag IS present)
-      name: "Android build"
-      language: python
-      python: 3.7
-      services:
-        - docker
-      script:
-        - sudo chown -R 1000:1000 .
-        # Output something every minute or Travis kills the job
-        - while sleep 60; do echo "=====[ $SECONDS seconds still running ]====="; done &
-        - ELECBUILD_COMMIT=HEAD ./contrib/android/build.sh
-        # kill background sleep loop
-        - kill %1
-        - ls -la dist
-        - if [ $(ls dist | grep -c Electrum-*) -eq 0 ]; then exit 1; fi
-      after_success: true
-      # disabled for now as travis started to always time out:
-    - if: false AND ((branch = master) OR (tag IS present))
-      name: "MacOS build"
-      os: osx
-      language: c
-      env:
-        - TARGET_OS=macOS
-      python: false
-      install:
-        - git fetch --all --tags
-      script: ./contrib/osx/make_osx
-      after_script: ls -lah dist && md5 dist/*
-      after_success: true
-    - if: (branch = master) OR (tag IS present)
-      name: "AppImage build"
-      language: c
-      python: false
-      services:
-        - docker
-      script:
-        - ELECBUILD_COMMIT=HEAD ./contrib/build-linux/appimage/build.sh
-      after_success: true
-    - if: (branch = master) OR (tag IS present)
-      name: "tarball build"
-      language: c
-      python: false
-      services:
-        - docker
-      script:
-        - ELECBUILD_COMMIT=HEAD ./contrib/build-linux/sdist/build.sh
-      after_success: true
-    - stage: release check
-      install:
-          - git fetch --all --tags
-      script:
-        - ./contrib/deterministic-build/check_submodules.sh
-      after_success: true
-      if: tag IS present