fix(two-factor): move `load_plugin_textdomain()` to `init`

[sjinks]

Description

WordPress Nightly now spits a doing-it-wrong deprecation warning when load_plugin_textdomain() is invoked too early (like in plugins_loaded).

This breaks our tests, such as E2E tests in VIP CLI.

For now, we fix the affected plugins locally and then create a PR to the upstream.

Ref: https://github.com/Automattic/vip-cli/actions/runs/11130390882/job/30929621217?pr=2045

Changelog Description

Fixed

• Two Factor plugin: address a deprecation warning about load_plugin_textdomain()

Pre-review checklist

Please make sure the items below have been covered before requesting a review:

• [x] This change works and has been tested locally or in Codespaces (or has an appropriate fallback).
• [ ] This change works and has been tested on a sandbox.
• [ ] This change has relevant unit tests (if applicable).
• [ ] This change uses a rollout method to ease deployment (if applicable - especially for large-scale actions requiring writes).
• [ ] This change has relevant documentation additions/updates (if applicable).
• [x] I've created a changelog description that aligns with the provided examples.

Pre-deploy checklist

• [ ] VIP staff: Ensure any alerts added/updated conform to internal standards (see internal documentation).

Steps to Test

Tests must pass.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 30.29%. Comparing base (3a9b969) to head (59f4b8a). Report is 13 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #5902 +/- ## ============================================= + Coverage 30.27% 30.29% +0.01% Complexity 4812 4812 ============================================= Files 287 287 Lines 20711 20699 -12 ============================================= Hits 6271 6271 + Misses 14440 14428 -12 ```

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