bundler plugin: Simplify retrieval of cpu count on OSX (#5180)

Calling awk is not necessary here, sysctl has the -n flag to print the value.
Signed-off-by: Clemens Gruber <clemensgru@gmail.com>

plugins/bundler/bundler.plugin.zsh

@@ -58,7 +58,7 @@ bundle_install() {
     if [[ $bundler_version > '1.4.0' || $bundler_version = '1.4.0' ]]; then
       if [[ "$OSTYPE" = darwin* ]]
       then
-        local cores_num="$(sysctl hw.ncpu | awk '{print $2}')"
+        local cores_num="$(sysctl -n hw.ncpu)"
       else
         local cores_num="$(nproc)"
       fi