docs: fix auth_tokens.create() docstring to use the real field and type

[arunpshankar]

The auth_tokens.create() docstring documents a config field and a type that do not exist. All four of its usage examples raise AttributeError if copied verbatim.

Reproduction

from google.genai import types

types.CreateAuthTokenConfig(
    uses=10,
    live_constrained_parameters=types.LiveEphemeralParameters(
        model="gemini-live-2.5-flash-preview",
    ),
)

AttributeError: module 'google.genai.types' has no attribute 'LiveEphemeralParameters'

Cause

The field on CreateAuthTokenConfig is live_connect_constraints, and the type is LiveConnectConstraints:

# google/genai/types.py
class CreateAuthTokenConfig(_common.BaseModel):
  ...
  live_connect_constraints: Optional[LiveConnectConstraints] = ...

LiveEphemeralParameters appears zero times in types.py. LiveConnectConstraints has the same (model, config) shape the examples already use, so this is a rename in the docs rather than a behaviour change.

What this PR changes

Docstring only, no functional change:

• live_constrained_parameters → live_connect_constraints (5 occurrences)
• types.LiveEphemeralParameters( → types.LiveConnectConstraints( (3 occurrences, Cases 2–4)
• prose comments referring to the old type name, and lockAdditionalFields → lock_additional_fields (the Python field name)
• adjacent typo attrubite → attribute, and lowercased the sentence continuation

Verification

All four corrected examples construct against google-genai 2.16.0:

Case 1 ✅   Case 2 ✅   Case 3 ✅   Case 4 ✅
4/4 corrected examples construct
original as-documented: AttributeError

Found while building a Vertex-based teaching repo — the examples were the first thing I reached for when wiring ephemeral tokens for a browser Live client.

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[arunpshankar]

Two notes from double-checking this before review:

1. The rename is already recorded in this repo. CHANGELOG.md:1447:

Rename LiveEphemeralParameters to LiveConnectConstraints. (6719faf)

So the docstring is stale text left behind by a deliberate rename, not a forward reference. LiveEphemeralParameters and live_constrained_parameters now appear only in this docstring and in generated docs — nowhere in the package source.

2. docs/genai.html carries the same stale examples (lines ~3710, 3742–3750, 3772, 3789, 3806). I have deliberately not touched it, since it is Sphinx build output rather than a source file — but it will need regenerating for the published docs to pick this up.

Safety of the change: the patch is docstring-only. Parsing both revisions and comparing the ASTs with docstrings stripped gives an identical tree, so there is no functional delta.