Replace __bridge_transfer with __bridge when convert from CFStringRef to NSString

[zhongwuzw]

New Pull Request Checklist

• I have read and understood the CONTRIBUTING guide

• I have read the Documentation

• I have searched for a similar pull request in the project and found none

• I have updated this branch with the latest master to avoid conflicts (via merge from master or rebase)

• I have added the required tests to prove the fix/feature I am adding

• I have updated the documentation (if necessary)

• I have run the tests and they pass

• I have run the lint and it passes (pod lib lint)

This merge request fixes / reffers to the following issues: ...

Pull Request Description

The same as #2392 .

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@98a2d9a). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #2394   +/-   ##
=========================================
  Coverage          ?   75.16%           
=========================================
  Files             ?       36           
  Lines             ?     3894           
  Branches          ?        0           
=========================================
  Hits              ?     2927           
  Misses            ?      967           
  Partials          ?        0

Impacted Files	Coverage Δ
SDWebImage/SDWebImageCoderHelper.m	61.59% <ø> (ø)
SDWebImage/SDWebImageGIFCoder.m	79.8% <100%> (ø)
SDWebImage/SDWebImageImageIOCoder.m	81.61% <100%> (ø)

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