docs(weave): document PII redaction from traces feature in Python SDK

[J2-D2-3PO]

Description

• Fixes https://wandb.atlassian.net/browse/DOCS-1211

Documents PII redaction feature v1 as described in #3406.
The new page will live at https://weave-docs.wandb.ai/guides/tracking/redact-pii

Depends on

#3406

Testing

• yarn start on local
• SME review

[circle-job-mirror]

Preview this PR with FeatureBee: https://beta.wandb.ai/?betaVersion=445ab4dd21721d6095e5acd431d0a3994ba32fc8

[J2-D2-3PO]

@anandwandb @niall-wb you are both tagged for review as SMEs, please review the docs PR for tech accuracy when the feature PR is ready to ship. A few notes:

• Comment on the PR with any requested changes / questions and I'll address.
• Feel free to add other SME reviewers if needed.
• Important: I used the PR description for feat(weave): PII Redaction for weave using Microsoft Presidio #3406 and internal feature doc to draft this, please help me to confirm that I'm not documenting anything not yet released and am fully documenting all user-facing functionality for v1 of this feature.

@scottire tagged you for review here too in case you want to see how this looks from the customer perspective, etc.