ci: Cleanup macOS runs

ci/lint/04_install.sh

@@ -6,22 +6,9 @@
 
 export LC_ALL=C
 
-if [ "$TRAVIS_OS_NAME" == "osx" ]; then
-  # update first to install required ruby dependency
-  travis_retry brew update
-  travis_retry brew reinstall git -- --with-pcre2 # for  --perl-regexp
-  travis_retry brew install grep # gnu grep for --perl-regexp support
-  PATH="$(brew --prefix grep)/libexec/gnubin:$PATH"
-  travis_retry brew install shellcheck
-  travis_retry brew upgrade python
-  PATH="$(brew --prefix python)/bin:$PATH"
-  export PATH
-else
-  SHELLCHECK_VERSION=v0.6.0
-  travis_retry curl --silent "https://storage.googleapis.com/shellcheck/shellcheck-${SHELLCHECK_VERSION}.linux.x86_64.tar.xz" | tar --xz -xf - --directory /tmp/
-  PATH="/tmp/shellcheck-${SHELLCHECK_VERSION}:${PATH}"
-  export PATH
-fi
-
 travis_retry pip3 install codespell==1.15.0
 travis_retry pip3 install flake8==3.7.8
+
+SHELLCHECK_VERSION=v0.6.0
+curl -s "https://storage.googleapis.com/shellcheck/shellcheck-${SHELLCHECK_VERSION}.linux.x86_64.tar.xz" | tar --xz -xf - --directory /tmp/
+export PATH="/tmp/shellcheck-${SHELLCHECK_VERSION}:${PATH}"