Update clean-up-environment.md

[AndreCNCampos]

Reviewed the Processes section and added BPT Governor information. Also changed the introduction of the section to better explain the need to perform maintenance on the BPT tables.

[outsystemsbot]

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[AndreCNCampos]

I read, understood and accept the OutSystems CLA.

[DanielNunesOS]

A note from discussing this with a TL in global support, and the owner of the BPT governor tool.
We could see that this article: https://success.outsystems.com/documentation/11/building_apps/using_processes_bpt/reseeding_identity_values_in_bpt_tables_sql_server/
Already has information on the BPT governor, mainly in the following paragraph:

Depending on the needs of the business, you can immediately purge tables of old processes. The OutSystems BPT API offers methods to help in the maintenance of BPT processes. Examples of this API being used are available in the Forge with tools such as DBCleaner, DBCleaner on Steroids, OneClickCLeanup, and BPT Governor.

We believe the changes in this PR could be discarded, but we believe this paragraph should be available in the Best practices for a tidy and clean environment article, instead of the Reseeding identity values in BPT tables - SQL Server article.

Let me know in slack if you need anything or help from my side, will gladly do.

Thank you