[PM-41628] Update email copy

[BTreston]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-41628

📔 Objective

updates email copy

📸 Screenshots

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

This PR updates the body copy of the provider user confirmation email in both the HTML and plain-text Handlebars templates, changing "This email is to notify you that you have been confirmed as a user of {{ProviderName}}" to "You've been confirmed as a user of {{ProviderName}}". The change also incidentally strips the UTF-8 BOM from both templates and adds a trailing newline to the text template, which brings them in line with the repository .editorconfig (charset = utf-8, insert_final_newline = true for non-.cs files). No template variables, escaping, or rendering logic were altered — {{ProviderName}} remains HTML-escaped by Handlebars and sanitized via CoreHelpers.SanitizeForEmail in HandlebarsMailService.SendProviderConfirmedEmailAsync. No tests or other code reference the previous copy string.

Code Review Details

No findings.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.04%. Comparing base (73ed2f6) to head (48e29db).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #8167       +/-   ##
===========================================
+ Coverage   15.10%   63.04%   +47.93%     
===========================================
  Files        1417     2315      +898     
  Lines       61422   100510    +39088     
  Branches     4901     9043     +4142     
===========================================
+ Hits         9279    63364    +54085     
+ Misses      51978    34957    -17021     
- Partials      165     2189     +2024     

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