Remove the .swift-version file

[mattrubin]

CocoaPods now supports specifying Swift versions in the podspec, so usage of this file by CocoaPods is deprecated.

Also, it appears this method of specifying a Swift version was never fully supported when integrating a pod into a project:

Note: While the pod author was initially allowed to publish their podspec using .swift-version file or --swift-version parameter, neither of them are preserved when a consumer is integrating their pod, therefore it is imperative to motivate pod authors to update their podspec to use the swift_versions DSL going forward.

CocoaPods/CocoaPods#8191 (comment)

[codecov]

Codecov Report

Merging #204 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #204   +/-   ##
========================================
  Coverage    99.34%   99.34%           
========================================
  Files            6        6           
  Lines          153      153           
========================================
  Hits           152      152           
  Misses           1        1

---

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[codecov]

Codecov Report

Merging #204 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #204   +/-   ##
========================================
  Coverage    99.34%   99.34%           
========================================
  Files            6        6           
  Lines          153      153           
========================================
  Hits           152      152           
  Misses           1        1

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0406db1...9692732. Read the comment docs.