fix(init): remove duplicated check

It was added due to #9039. See https://github.com/ohmyzsh/ohmyzsh/pull/11400#pullrequestreview-1223587420

oh-my-zsh.sh

@@ -57,9 +57,7 @@ mkdir -p "$ZSH_CACHE_DIR/completions"
 (( ${fpath[(Ie)"$ZSH_CACHE_DIR/completions"]} )) || fpath=("$ZSH_CACHE_DIR/completions" $fpath)
 
 # Check for updates on initial load...
-if [[ "$DISABLE_AUTO_UPDATE" != true ]]; then
-  source "$ZSH/tools/check_for_upgrade.sh"
-fi
+source "$ZSH/tools/check_for_upgrade.sh"
 
 # Initializes Oh My Zsh