Regenerate proto files

[jarifibrahim]

The proto files in the current master are not compatible with the ones in dgraph. See build for PR hypermodeinc/dgraph#4200

	[Step 3/5] # github.com/dgraph-io/dgraph/protos/pb
[11:02:11]	[Step 3/5] ../protos/pb/pb.pb.go:7146:29: m.Kv[iNdEx].MarshalToSizedBuffer undefined (type *pb.KV has no field or method MarshalToSizedBuffer)
[11:02:11]	[Step 3/5] ../protos/pb/pb.pb.go:7209:29: m.Kv[iNdEx].MarshalToSizedBuffer undefined (type *pb.KV has no field or method MarshalToSizedBuffer)
[11:02:40]	[Step 3/5] Makefile:66: recipe for target 'install' failed
[11:02:40]	[Step 3/5] make[1]: *** [install] Error 2
[11:02:40]	[Step 3/5] make[1]: Leaving directory '/home/pawan0201/go/src/github.com/dgraph-io/dgraph/dgraph'
[11:02:40]	[Step 3/5] make: *** [install] Error 2
[11:02:40]	[Step 3/5] Makefile:43: recipe for target 'install' failed
[11:02:40]	[Step 3/5] Process exited with code 2

https://teamcity.dgraph.io/viewLog.html?buildId=29232&buildTypeId=Dgraph_Blockade&tab=buildLog

This PR the proto files in badger. I've run ./gen.sh script to regenerate these.

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[coveralls]

Coverage decreased (-0.03%) to 77.449% when pulling 4037482 on ibrahim/proto-update into b9056f1 on master.