[Security] Bump mail from 2.5.4 to 2.5.5

[dependabot-preview]

Bumps mail from 2.5.4 to 2.5.5. This update includes security fixes.

Vulnerabilities fixed

SMTP command injection
Because Mail does not disallow CRLF in email addresses, an attacker can
inject SMTP commands in specially crafted email addresses passed to
RCPT TO and MAIL FROM.

Not affected by this vulnerability:

• Ruby 2.4.0+ with a fix for CVE-2015-9096.
• Applications that do not use SMTP delivery.
• Applications that validate email addresses to not include CRLF.

The injection attack is described in Terada, Takeshi. "SMTP Injection via
Recipient Email Addresses." 2015. The attacks described in the paper
(Terada, p. 4) can be applied to the library without any modification.

Patched versions: [">= 2.5.5"]
Unaffected versions: []

Changelog

Sourced from mail's changelog.

== Version 2.8.0 (unreleased)

Breaking changes:

• Message#without_attachments! now deletes nested attachments. (TylerRick)
• Sendmail and exim delivery now raise DeliveryError when the command exits with a nonzero exitstatus. (benmmurphy, CoolElvis)
• Sendmail and exim delivery :arguments option must be an array of string args. (benmmurphy)
• Passing unparsed headers to Mail::Field.new is no longer supported. Use Mail::Field.parse. (jeremy)
• Removed long-deprecated features: Message#register_for_delivery_notification, #has_transfer_encoding?, #add_transfer_encoding, #transfer_encoding, #message_content_type, #mime_parameters, #encode!, and Part#inline_content_id. (jeremy)

Compatibility:

• Handle a wide variety of non-RFC Message-ID formats. (peterkovacs)
• Gracefully parse invalid dates in Date and Received headers. (okkez)
• Converting to multipart moves Content-* headers to the new part. (kirikak2)
• Multipart Content-Type no longer includes a needless charset param. (kirikak2)
• Replies prefix subject with "Re: " instead of "RE: " per 5322 3.6.5. (mashedcode)

Features:

• Message#inspect_structure and PartsList#inspect_structure pretty-print the hierarchy of message parts. (TylerRick)

Please check 2-7-stable for previous changes.

Commits

• 97a8548 2.5.5 release
• 63fb41b Always use an SSL context. [Fixes #548]
• f84b84d Specs: fix missing should_receive from f60ccc660434d445b78e8281833c99048a00de20
• f60ccc6 Fix Mail::Exim, forgotten in 4875bc2b
• 527067d Gemfile: no rdoc 5 on Ruby 1.9.2
• 396d39f Clamp down allowed gem versions depending on Ruby version supported
• b9cee02 Specs: fix expect-style that wasn't backported to old should-style
• b5a2884 Backport fixes for specs on Ruby 1.9.3+
• 6110413 Fix tested Ruby versions in README
• ddc85ed use latest ruby version in CI
• Additional commits viewable in compare view

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