fix(git): add vendor in .gitignore

vendor/google.golang.org/grpc/MAINTAINERS.md

@@ -1,27 +0,0 @@
-This page lists all active maintainers of this repository. If you were a
-maintainer and would like to add your name to the Emeritus list, please send us a
-PR.
-
-See [GOVERNANCE.md](https://github.com/grpc/grpc-community/blob/master/governance.md)
-for governance guidelines and how to become a maintainer.
-See [CONTRIBUTING.md](https://github.com/grpc/grpc-community/blob/master/CONTRIBUTING.md)
-for general contribution guidelines.
-
-## Maintainers (in alphabetical order)
-- [canguler](https://github.com/canguler), Google LLC
-- [cesarghali](https://github.com/cesarghali), Google LLC
-- [dfawley](https://github.com/dfawley), Google LLC
-- [easwars](https://github.com/easwars), Google LLC
-- [jadekler](https://github.com/jadekler), Google LLC
-- [menghanl](https://github.com/menghanl), Google LLC
-- [srini100](https://github.com/srini100), Google LLC
-
-## Emeritus Maintainers (in alphabetical order)
-- [adelez](https://github.com/adelez), Google LLC
-- [iamqizhao](https://github.com/iamqizhao), Google LLC
-- [jtattermusch](https://github.com/jtattermusch), Google LLC
-- [lyuxuan](https://github.com/lyuxuan), Google LLC
-- [makmukhi](https://github.com/makmukhi), Google LLC
-- [matt-kwong](https://github.com/matt-kwong), Google LLC
-- [nicolasnoble](https://github.com/nicolasnoble), Google LLC
-- [yongni](https://github.com/yongni), Google LLC