ci: add macOS 11 Big Sur

Remove all traces of Travis CI

Change-Id: I1839ae96e41678f722cba052a56ae7c54255defd
diff --git a/.jenkins.d/00-deps.sh b/.jenkins.d/00-deps.sh
index 90f7bb4..00b9a5d 100755
--- a/.jenkins.d/00-deps.sh
+++ b/.jenkins.d/00-deps.sh
@@ -3,16 +3,13 @@
 
 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 [[ $JOB_NAME == *"Docs" ]]; then
         FORMULAE+=(doxygen graphviz)
     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"