add release notes for Faraday v0.17.1

[technoweenie]

Ship Faraday v0.17.1.

Release notes preview:

Final release before Faraday v1.0, with important fixes for Ruby 2.7.

Fixes:

• RaiseError response middleware raises exception if HTTP client returns a nil
  status. (Raise exception on nil status #1042)

Misc:

• Fix Ruby 2.7 warnings (This fixes warnings on Ruby 2.7 #1009)
• Add Faraday::Deprecate to warn about upcoming v1.0 changes. (Create faraday deprecation class #1054, 0.1x deprecate fixes #1059,
  0.1x deprecate fixes 2 #1076, Remove the intermediate variable #1077)
• Add release notes up to current in CHANGELOG.md (Add release notes from v0.9.2 - v0.17.0 to the Changelog #1066)
• Port minimal rspec suite from main branch to run backported tests. (0.1x spec #1058)