Bump psutil from 5.4.5 to 5.6.6

Bumps [psutil](https://github.com/giampaolo/psutil) from 5.4.5 to 5.6.6.
- [Release notes](https://github.com/giampaolo/psutil/releases)
- [Changelog](https://github.com/giampaolo/psutil/blob/master/HISTORY.rst)
- [Commits](giampaolo/psutil@release-5.4.5...release-5.6.6)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -8,7 +8,7 @@ jsonrpcclient==2.5.2
 jsonrpcserver==3.5.4
 jsonrpc-async==0.6
 numpy==1.15.1
-psutil==5.4.5
+psutil==5.6.6
 python-rocksdb==0.6.9
 requests==2.20.0
 aiohttp_cors==0.7.0