vagrant: darwin64: backport some tunings from master

git is already there, don't brew upgrade for better speed.

Vagrantfile

@@ -57,9 +57,9 @@ def packages_darwin
     sudo softwareupdate --install --all
     which brew || CI=1 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
     brew update > /dev/null
-    brew install pkg-config readline openssl@1.1 zstd lz4 xz git
+    brew install pkg-config readline openssl@1.1 zstd lz4 xz
     brew install --cask macfuse
-    brew upgrade  # upgrade everything
+    # brew upgrade  # upgrade everything (takes rather long)
     echo 'export PKG_CONFIG_PATH=/usr/local/opt/openssl@1.1/lib/pkgconfig' >> ~vagrant/.bash_profile
   EOF
 end