Bump cocoapods-downloader from 1.4.0 to 1.6.3 in /dev/ci/mac

Bumps [cocoapods-downloader](https://github.com/CocoaPods/cocoapods-downloader) from 1.4.0 to 1.6.3.
- [Release notes](https://github.com/CocoaPods/cocoapods-downloader/releases)
- [Changelog](https://github.com/CocoaPods/cocoapods-downloader/blob/master/CHANGELOG.md)
- [Commits](CocoaPods/cocoapods-downloader@1.4.0...1.6.3)

---
updated-dependencies:
- dependency-name: cocoapods-downloader
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

dev/ci/mac/Gemfile.lock

@@ -43,7 +43,7 @@ GEM
       public_suffix
       typhoeus (~> 1.0)
     cocoapods-deintegrate (1.0.4)
-    cocoapods-downloader (1.4.0)
+    cocoapods-downloader (1.6.3)
     cocoapods-plugins (1.0.0)
       nap
     cocoapods-search (1.0.0)