[Brave Leo]: Update model names in Leo models menu

[LorenzoMinto]

Description

We should update the model names in the model menu:

• "Llama 3 8B" -> "Llama 3.1 8B"
• "Claude 3 Sonnet" -> "Claude 3.5 Sonnet"

Current result

cc @mattmcalister @stephendonner

[kjozwiak]

The above requires 1.69.157 or higher for 1.69.x verification 👍

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.69.157 Chromium: 128.0.6613.85 (Official Build) (64-bit)
-- | --
Revision | 14c4bb724553b882abcd2fccd9b5acf1f177fe6d
OS | Windows 10 Version 22H2 (Build 19045.4780)

Using the STR/Cases outlined via #40464 (comment), ensured that the new strings were being used as per the following:

Example	Example

[hffvld]

Verified on Pixel 7 using version(s):

Device/OS: Pixel 7 / panther_beta-user 15 AP41.240726.009 release-keys
Brave build: 1.69.157
Chromium: 128.0.6613.85 (Official Build) (64-bit) 

---

STEPS:

1. Launch Leo
2. Hamburger menu > Leo
3. ⚙️ > Verify
4. Advanced Settings
5. Default model for new conversations > Verify

ACTUAL RESULTS:

• Verified that Llama 3 8B updated to Llama 3.1 8B
• Verified that Claude 3 Sonnet updated to Claude 3.5 Sonnet

---

1	2

[kjozwiak]

Verification PASSED on iPhone 11 running iOS 17.6 using the following build(s):

Brave | 1.69.162 Chromium: 128.0.6613.120 (Official Build) stable (64-bit)
--- | ---
Revision | e534755d4eb5...
OS | iOS

Using the STR/Cases outlined via brave/brave-core#25343 (comment), ensured that the correct strings/text was being used as per the following:

• Llama 3 8B --> Llama 3.1 8B
• Claude 3 Sonnet --> Claude 3.5 Sonnet

Example	Example