[Security Solution] Enable the feature flag for JSON diffing in prebu…

…ilt rules (#173368)

**Ticket:** #169160

## Summary

Sets the `jsonPrebuiltRulesDiffingEnabled` to `true` to enable the new
"Updates" tab in prebuilt rules flyout.

### IMPORTANT: Merge only once acceptance and exploratory testing are
passed!

<img width="1178" alt="Scherm­afbeelding 2023-12-13 om 17 37 07"
src="https://github.com/elastic/kibana/assets/15949146/9e07e069-595f-49a6-98c2-d2ed4aa3f977">

Co-authored-by: Georgii Gorbachev <[email protected]>

x-pack/plugins/security_solution/common/experimental_features.ts

@@ -162,7 +162,7 @@ export const allowedExperimentalValues = Object.freeze({
    * This tab shows the JSON diff between the installed prebuilt rule
    * version and the latest available version.
    */
-  jsonPrebuiltRulesDiffingEnabled: false,
+  jsonPrebuiltRulesDiffingEnabled: true,
 });
 
 type ExperimentalConfigKeys = Array<keyof ExperimentalFeatures>;