AndroidManifest references android-8
AndroidManifest references android-8

Summary:
Previously, AndroidManifest.xml referenced android-7, which is
not compatible with building the sdk.  IntelliJ and ant builds
appear to have ignored this, but Eclipse fails.

This moves AndroidManifest.xml to reference android-8 instead.

Test Plan:
- build in Eclipse
- build all samples
- run unit tests

Revert Plan:
- safe

Tags:

Reviewers: clang, karthiks, mingfli

Reviewed By: clang

CC: msimpson

Differential Revision: https://phabricator.fb.com/D589371

Task ID: 1777642

bitcellar-labs/facebook-android-sdk,satoshi-okawa/facebook-android-sdk-test1,taisukeoe/facebook-android-sdk,MarkHappy/Facebook_SDK,TimeIncOSS/facebook-android-sdk,mindjolt/facebook-android-sdk,couchbaselabs/facebook-android-sdk,minhduc3404/facebookSdk,TechSmith/facebook-android-sdk,minhduc3404/facebookSdk,PioneerLab/facebook-android-sdk,quizlet/facebook-android-sdk,bitcellar-labs/facebook-android-sdk,lizhi5753186/facebook-android-sdk,CristianOliveiraDaRosa/facebook-android-sdk,CristianOliveiraDaRosa/facebook-android-sdk,couchbaselabs/facebook-android-sdk,scalio/facebook-android-sdk,lizhi5753186/facebook-android-sdk,ribot/facebook-android-sdk,Flutterbee/facebook-android-sdk,ribot/facebook-android-sdk,GrioSF/facebook-android-sdk,MKrishtop/facebook-android-sdk,PioneerLab/facebook-android-sdk,Limbika/facebook-android-sdk,RabbleApp/facebook-android-sdk,mindjolt/facebook-android-sdk,taisukeoe/facebook-android-sdk,Flutterbee/facebook-android-sdk,MarkHappy/Facebook_SDK,scalio/facebook-android-sdk,GrioSF/facebook-android-sdk,RabbleApp/facebook-android-sdk,Limbika/facebook-android-sdk,TechSmith/facebook-android-sdk,TimeIncOSS/facebook-android-sdk,quizlet/facebook-android-sdk,satoshi-okawa/facebook-android-sdk-test1,MKrishtop/facebook-android-sdk