Fix bug related to swift change in error string conversion

[MrLotU]

Due to a change in Swift, all Errors became CustomStringConvertible by virtue of implicit bridging with NSError. The check for CustomStringConvertible conformance has been removed. This restores the previous behavior and makes the tests pass again.

Unblocks #67

[codecov-commenter]

Codecov Report

Merging #68 into master will increase coverage by 0.07%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #68      +/-   ##
==========================================
+ Coverage   94.58%   94.66%   +0.07%     
==========================================
  Files          23       23              
  Lines        1182     1180       -2     
==========================================
- Hits         1118     1117       -1     
+ Misses         64       63       -1     

Flag	Coverage Δ
#unittests	94.66% <ø> (+0.07%)	:arrow_up:

Impacted Files	Coverage Δ
...syncKit/EventLoopFuture/EventLoopFutureQueue.swift	100.00% <ø> (+2.94%)	:arrow_up:

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[calebkleveter]

I can't reproduce this locally on the latest versions of Catalina, Xcode, and Swift. 🤔

[MrLotU]

CI fails on MacOS right here: https://github.com/vapor/async-kit/pull/67/checks?check_run_id=730187317#step:4:229 I can see if I can repro locally 🤔

[gwynne]

Oh look, weird magical unwanted NSError bridging strikes again...

[gwynne]

@MrLotU Suggested PR body for release notes:

---

• Due to a change in Swift, all Errors became CustomStringConvertible by virtue of implicit bridging with NSError. The check for CustomStringConvertible conformance has been removed. This restores the previous behavior and makes the tests pass again.

• Unblocks #67

[tanner0101]

These changes are now available in 1.1.1