ci: add macOS 11 Big Sur

Remove all traces of Travis CI

Change-Id: Ic0a802db8a2ec5dfef093321b3bc0a7c736b5a5c
diff --git a/.jenkins.d/00-deps.sh b/.jenkins.d/00-deps.sh
index 304a19a..31b89ee 100755
--- a/.jenkins.d/00-deps.sh
+++ b/.jenkins.d/00-deps.sh
@@ -3,13 +3,10 @@
 
 if has OSX $NODE_LABELS; then
     FORMULAE=(boost openssl pkg-config)
-    if has OSX-10.13 $NODE_LABELS || has OSX-10.14 $NODE_LABELS; then
-        FORMULAE+=(python)
-    fi
 
-    if [[ -n $GITHUB_ACTIONS || -n $TRAVIS ]]; then
-        # GitHub Actions and Travis images come with a large number of
-        # pre-installed packages. Don't waste time upgrading all of them.
+    if [[ -n $GITHUB_ACTIONS ]]; then
+        # GitHub Actions runners have a large number of pre-installed
+        # Homebrew packages. Don't waste time upgrading all of them.
         brew list --versions "${FORMULAE[@]}" || brew update
         for FORMULA in "${FORMULAE[@]}"; do
             brew list --versions "$FORMULA" || brew install "$FORMULA"