Updated painless-walkthrough documentation (#65530)

Update documentation about regex note.

docs/painless/painless-guide/painless-walkthrough.asciidoc

@@ -206,14 +206,13 @@ GET hockey/_search
 [[modules-scripting-painless-regex]]
 ==== Regular expressions
 
-NOTE: Regexes are disabled by default because they circumvent Painless's
-protection against long running and memory hungry scripts. To make matters
-worse even innocuous looking regexes can have staggering performance and stack
-depth behavior. They remain an amazing powerful tool but are too scary to enable
-by default. To enable them yourself set `script.painless.regex.enabled: true` in
-`elasticsearch.yml`. We'd like very much to have a safe alternative
-implementation that can be enabled by default so check this space for later
-developments!
+NOTE: Regexes are enabled by default as the Setting `script.painless.regex.enabled` 
+has a new option, `limited`, the default. This defaults to using regular expressions 
+but limiting the complexity of the regular expressions. Innocuous looking regexes 
+can have staggering performance and stack depth behavior. But still, they remain an 
+amazingly powerful tool. In addition, to `limited`, the setting can be set to `true`, 
+as before, which enables regular expressions without limiting them.To enable them 
+yourself set `script.painless.regex.enabled: true` in `elasticsearch.yml`.
 
 Painless's native support for regular expressions has syntax constructs: