Edit TypeScript style guideline to ban engineers to write TS code at the initial phase of the migration

[hayata-suenaga]

Add an instruction to ban new code to be written in TypeScript in the initial phase of the migration.

As par this Slack conversation (internal link), we don't want any engineers outside the migration team to write TypeScript code at this point.

[melvin-bot]

Reviewing label has been removed, please complete the "BugZero Checklist".

[melvin-bot]

The solution for this issue has been 🚀 deployed to production 🚀 in version 1.3.54-13 and is now subject to a 7-day regression period 📆. Here is the list of pull requests that resolve this issue:

• Edit TS Style Guide to ban new TS code #24439

If no regressions arise, payment will be issued on 2023-08-24. 🎊

After the hold period is over and BZ checklist items are completed, please complete any of the applicable payments for this issue, and check them off once done.

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