Increase iOS deployment target to 9.0 the minimum supported by Xcode 12

The CPDAcknowledgements.podspec declares as deployment target 8.0 but the minimum support by Xcode 12 is 9.0. So we need update it:

`s.ios.deployment_target` = '9.0'`

Now if we include this pod it produces the following error:

`
The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 14.3.99.
`

Update CPDAcknowledgements.podspec, where the iOS deployment target is declared. Change s.ios.deployment_target from 8.0 to 9.0, then include the pod with Xcode 12 and confirm the deployment-target warning is gone.

Written by the indexing model from the issue text.