chore: reduce mixpanel recording sessions (#40881)

## Description
We are reducing the amount of sessions that get recorded on Mixpanel


https://docs.mixpanel.com/docs/session-replay/implement-session-replay/session-replay-web#sampling

/test Sanity

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Chores**
- Reduced the percentage of session recordings captured for analytics
from 100% to 50%.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

<!-- This is an auto-generated comment: Cypress test results  -->
> [!IMPORTANT]
> 🟣 🟣 🟣 Your tests are running.
> Tests running at:
<https://github.com/appsmithorg/appsmith/actions/runs/15484615083>
> Commit: 5b875fb848e58cad2f2b55f1f40cf2e54ec3a5b4
> Workflow: `PR Automation test suite`
> Tags: `@tag.Sanity`
> Spec: ``
> <hr>Fri, 06 Jun 2025 06:51:16 UTC
<!-- end of auto-generated comment: Cypress test results  -->

app/client/src/utils/Analytics/mixpanel.ts

@@ -44,7 +44,7 @@ class MixpanelSingleton {
       if (mixpanel.enabled) {
         this.mixpanel = loadedMixpanel;
         this.mixpanel.init(mixpanel.apiKey, {
-          record_sessions_percent: 100,
+          record_sessions_percent: 50,
           record_block_selector: mask ? ".mp-block" : "",
           record_mask_text_selector: mask ? ".as-mask" : "",
         });