Remove deprecated integration tests from README.md (facebook#11354)

Summary:
The CI systems other than CircleCI are almost always in a failing state. Since CircleCI covers linux, macos, and windows, we can remove the others.

Pull Request resolved: facebook#11354

Reviewed By: hx235

Differential Revision: D44774627

Pulled By: ajkr

fbshipit-source-id: c83b298ec5afe4ea410744eda6cc98fc6a3365f1

Author: nccx

README.md

@@ -1,8 +1,6 @@
 ## RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
 
 [![CircleCI Status](https://circleci.com/gh/facebook/rocksdb.svg?style=svg)](https://circleci.com/gh/facebook/rocksdb)
-[![Appveyor Build status](https://ci.appveyor.com/api/projects/status/fbgfu0so3afcno78/branch/main?svg=true)](https://ci.appveyor.com/project/Facebook/rocksdb/branch/main)
-[![PPC64le Build Status](http://140-211-168-68-openstack.osuosl.org:8080/buildStatus/icon?job=rocksdb&style=plastic)](http://140-211-168-68-openstack.osuosl.org:8080/job/rocksdb)
 
 RocksDB is developed and maintained by Facebook Database Engineering Team.
 It is built on earlier work on [LevelDB](https://github.com/google/leveldb) by Sanjay Ghemawat (sanjay@google.com)