drop travis ci support

.travis.yml

@@ -1,39 +0,0 @@
-version: ~> 1.0
-import: nix-community/nix-travis-ci:nix.yml@main
-
-sudo: false
-
-env:
-  global:
-    # Set this to cache your build results in cachix for faster builds
-    # in travis and for everyone who uses your cache.
-    #
-    # Format: Your cachix cache host name without the ".cachix.org" suffix.
-    # Example: mycache (for mycache.cachix.org)
-    #
-    # For this to work, you also need to set the  CACHIX_SIGNING_KEY
-    # in your repository settings in Travis.
-    # - CACHIX_CACHE=
-    # Set this to notify the global nur package registry that changes are
-    # available.
-    #
-    # The repo name as used in
-    # https://github.com/nix-community/NUR/blob/master/repos.json
-    - NUR_REPO="<YOUR_NUR_REPO_NAME_HERE>"
-
-matrix:
-  include:
-    - env: NIX_PATH=nixpkgs=channel:nixpkgs-unstable
-    - env: NIX_PATH=nixpkgs=channel:nixos-unstable
-    - env: NIX_PATH=nixpkgs=channel:nixos-22.11
-
-script:
- - nix-build ci.nix -A buildOutputs
- - nix eval -f default.nix 'lib'
- - nix eval -f default.nix 'modules'
- - nix eval -f default.nix 'overlays'
-
-after_success:
-  - if [ -n "${CACHIX_CACHE}" ]; then nix-build ci.nix -A cacheOutputs | cachix push "${CACHIX_CACHE}"; fi
-  - if [[ NUR_REPO != "<YOUR_NUR_REPO_NAME_HERE>" && "cron" != "${TRAVIS_EVENT_TYPE}" && "false" = "${TRAVIS_PULL_REQUEST}" && "master" = "${TRAVIS_BRANCH}" ]]; then
-      curl -XPOST "https://nur-update.herokuapp.com/update?repo=${NUR_REPO}"; fi