feat(python): Add missing sensitive data examples (#14415)

[This
section](https://docs.sentry.io/platforms/python/data-management/sensitive-data/#examples)
in the Python docs is currently showing JS examples. Adding the missing
examples in Python.

Author: sentrivana

platform-includes/sensitive-data/set-tag/python.mdx

@@ -0,0 +1,3 @@
+```python
+sentry_sdk.set_tag("birthday", checksum_or_hash("08/12/1990"))
+```

platform-includes/sensitive-data/set-user/python.mdx

@@ -0,0 +1,7 @@
+```python
+sentry_sdk.set_user({"id": user.id})
+
+# or
+
+sentry_sdk.set_user({"username": user.username})
+```