message: adjust travis ci build badge
diff: VelocyPack (VPack) - a fast and compact format for serialization and storage
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  -TravisCI: [![Build Status](https://secure.travis-ci.org/arangodb/velocypack.png?branch=main)](http://travis-ci.org/arangodb/velocypack) AppVeyor: [![Build status](https://ci.appveyor.com/api/projects/status/pkbl4t7vey88bqud?svg=true)](https://ci.appveyor.com/project/jsteemann/velocypack) Coveralls: [![Coverage Status](https://coveralls.io/repos/arangodb/velocypack/badge.svg?branch=main&service=github)](https://coveralls.io/github/arangodb/velocypack?branch=main)
  +TravisCI: [![Build Status](https://api.travis-ci.com/arangodb/velocypack.svg?branch=main)](https://travis-ci.com/arangodb/velocypack) AppVeyor: [![Build status](https://ci.appveyor.com/api/projects/status/pkbl4t7vey88bqud?svg=true)](https://ci.appveyor.com/project/jsteemann/velocypack) Coveralls: [![Coverage Status](https://coveralls.io/repos/arangodb/velocypack/badge.svg?branch=main&service=github)](https://coveralls.io/github/arangodb/velocypack?branch=main)
  Motivation
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