fix(updater): give priority to `zstyle` settings if set (#10587)

Fixes #10587

tools/check_for_upgrade.sh

@@ -10,11 +10,13 @@ fi
 # - auto: the update is performed automatically when it's time
 # - reminder: a reminder is shown to the user when it's time to update
 # - disabled: automatic update is turned off
-zstyle -s ':omz:update' mode update_mode || update_mode=prompt
+zstyle -s ':omz:update' mode update_mode || {
+  update_mode=prompt
 
-# Support old-style settings
-[[ "$DISABLE_UPDATE_PROMPT" != true ]] || update_mode=auto
-[[ "$DISABLE_AUTO_UPDATE" != true ]] || update_mode=disabled
+  # If the mode zstyle setting is not set, support old-style settings
+  [[ "$DISABLE_UPDATE_PROMPT" != true ]] || update_mode=auto
+  [[ "$DISABLE_AUTO_UPDATE" != true ]] || update_mode=disabled
+}
 
 # Cancel update if:
 # - the automatic update is disabled.