Small text change to Leo opt-in copy

[mattmcalister]

Description

The current Leo opt-in modal refers to the Mixtral model, but we are changing the default. We should update the language to be more abstract.

Steps to reproduce

1. New profile
2. Open Leo panel
3. Begin a conversation
4. See consent language

Actual result

Expected result

This issue proposes to change the text to "The default model will change from time to time." It also updates the Help Center link from the Leo section home to the specific article on LLMs: What are the differences between Leo's AI Models? https://support.brave.com/hc/en-us/articles/26727364100493-What-are-the-differences-between-Leo-s-AI-Models

Reproduces how often

Easily reproduced

Desktop Brave version (brave://version info)

1.76.24 Chromium: 132.0.6834.83 (Official Build) nightly (arm64)

Android device

• Brand/model:
• Android version:

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

Policy review for this change: https://github.com/brave/reviews/issues/1830 (closed)

[hffvld]

Verified on Pixel 6 using version(s):

Device/OS: Pixel 6 / oriole-user 15 AP4A.241205.013 release-keys
Brave build: 1.76.52 
Chromium: 133.0.6943.54 (Official Build) beta (64-bit) 

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STEPS:

1. Follow the STR/TP from Small text change to Leo opt-in copy #43413 (comment)
2. Verify

ACTUAL RESULTS:

• Verified that The default model for all users is currently Mixtral 8x7B. string was updated to The default model will change from time to time.
• Verified that Brave wiki was updated to Brave Help Center URL.

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Old strings/URL	Updated strings/URL

[MadhaviSeelam]

Verification PASSED using

Brave | 1.76.58 Chromium: 133.0.6943.98 (Official Build) beta (64-bit)
-- | --
Revision | e6c9f3240b1045e0f4bcb1301b9a0d7cda5684f8
OS | Windows 11 Version 24H2 (Build 26100.2894)

1. Installed 1.76.58
2. launched Brave
3. clicked on Leo icon to open Leo panel
4. entered "BAT" in the input field
5. consent page shown as expected

• Confirmed the text "The default model for all users is currently Mixtral 8x7B" was updated to "The default model will change from time to time."
• Confirmed Brave Wiki link is replaced with Brave Help Center link
• Confirmed when clicked Brave Help center link, navigated to https://support.brave.com/hc/en-us/articles/26727364100493-What-are-the-differences-between-Leo-s-AI-Models

1.75.x	1.76.x