[deps] Tools: Update MailKit to 4.15.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
MailKit (source)	4.14.1 → 4.15.0

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Release Notes

jstedfast/MailKit (MailKit)

v4.15.0

Compare Source

• Default the SmtpClient/Pop3Client/ImapClient.SslProtocols to the ServicePointManager.SecurityProtocol
  value in .NET Framework (net4x). (issue #​1952)
• Added support for.NET 10.
• Marked IMailService.SslCipherAlgorithm, SslCipherStrength, SslHashAlgorithm, SslHashStrength,
  SslKeyExchangeAlgorithm, and SslKeyExchangeStrength as Obsolete in .NET 10 in favor of the
  IMailService.SslCipherSuite property (.NET 10 only).
• Bumped MimeKit dependency to 4.15.0.

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Configuration

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[bitwarden-bot]

Internal tracking:

• ID: PM-32935
• Link: https://bitwarden.atlassian.net/browse/PM-32935

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.45%. Comparing base (d1a5c4d) to head (12a4370).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7115   +/-   ##
=======================================
  Coverage   56.45%   56.45%           
=======================================
  Files        2013     2013           
  Lines       88098    88098           
  Branches     7860     7860           
=======================================
  Hits        49739    49739           
  Misses      36543    36543           
  Partials     1816     1816           

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