message: ci: Drop Travis-specific workaround for shellcheck
diff: export LC_ALL=C
  -# The shellcheck binary segfault/coredumps in Travis with LC_ALL=C
  -# It does not do so in Ubuntu 14.04, 16.04, 18.04 in versions 0.3.3, 0.3.7, 0.4.6
  -# respectively. So export LC_ALL=C is set as required by lint-shell-locale.sh
  -# but unset here in case of running in Travis.
  -if [ "$TRAVIS" = "true" ]; then
  - unset LC_ALL
  -fi
  -
  # Disabled warnings:
  disabled=(
  SC2046 # Quote this to prevent word splitting.
  