varstash: no need to use regex, avoids 'failed to load module: zsh/regex' error

lib/varstash

@@ -231,7 +231,7 @@ function stash() {
 function autostash() {
     local run_from_autostash=1
     while [[ -n $1 ]]; do
-        if [[ $1 == "alias" && $2 =~ "=" ]]; then
+        if [[ $1 == "alias" && $2 = *=* ]]; then
             shift
             local _stashing_alias_assign=1
         fi