Remove dead "Show hex data" setting from Advanced Settings

## **Description**

The "Show hex data" toggle in Advanced Settings (`app/components/Views/Settings/AdvancedSettings/index.js`) is dead code. The setting value (`state.settings.showHexData`) is no longer read by any component in the app, so toggling it has no effect.

The consumers were removed in:
- **PR #24476** — removed the legacy send flow that read `showHexData` to conditionally show a hex data input
- **PR #24929** — removed the legacy confirmation view that read `showHexData` to conditionally show a hex data modal

The redesigned confirmation views do not use this setting.

## **Technical Details**

The following dead code should be removed:

- **Settings toggle:** `app/components/Views/Settings/AdvancedSettings/index.js` — remove the `showHexData` prop, the `SettingsRow` for "Show hex data", and the `mapStateToProps`/`mapDispatchToProps` wiring
- **Action creator:** `app/actions/settings/index.js` — remove `setShowHexData`
- **Reducer:** `app/reducers/settings/index.js` — remove the `SET_SHOW_HEX_DATA` case
- **Locale strings:** remove `app_settings.show_hex_data` and `app_settings.hex_desc` from all locale files
- **Test/mock references:** update `AdvancedSettings/index.test.tsx` and `Perps/__mocks__/perpsStateMock.ts`

## **Threat Modeling Framework**

- **What are we working on?** Removing dead UI and code that no longer has any effect.
- **What can go wrong?** Very low risk — the setting is already unused. The only concern is ensuring no other code path reads `showHexData` (confirmed: none do).
- **What are we going to do about it?** Remove all references and verify tests pass.
- **Did we do a good job?** Verify the toggle is gone from Advanced Settings and no regressions in settings or confirmation flows.

## **Acceptance Criteria**

- [ ] The "Show hex data" toggle is removed from Advanced Settings
- [ ] The `showHexData` Redux state, action, and reducer are removed
- [ ] Related locale strings are removed from all language files
- [ ] Tests and mocks are updated accordingly
- [ ] No regressions in Advanced Settings or confirmation flows

## **References**

- PR #24476 — `fix: Remove legacy send flow, components and tests`
- PR #24929 — `chore: remove legacy confirmation code`
- Files to clean up:
- `app/components/Views/Settings/AdvancedSettings/index.js`
- `app/actions/settings/index.js`
- `app/reducers/settings/index.js`
- `app/components/Views/Settings/AdvancedSettings/index.test.tsx`
- `app/components/UI/Perps/__mocks__/perpsStateMock.ts`
- `locales/languages/*.json` (all locale files)

Start by searching for showHexData and read the listed AdvancedSettings component, settings action and reducer, test, mock, and locale files. Run AdvancedSettings/index.test.tsx after removing the toggle and related references; done means no showHexData references remain and the settings and confirmation-flow tests pass.

Written by the indexing model from the issue text.