Bump psutil from 2.1.1 to 5.6.6 in /Holmes/fuzzers

Bumps [psutil](https://github.com/giampaolo/psutil) from 2.1.1 to 5.6.6.
- [Changelog](https://github.com/giampaolo/psutil/blob/master/HISTORY.rst)
- [Commits](giampaolo/psutil@release-2.1.1...release-5.6.6)

---
updated-dependencies:
- dependency-name: psutil
  dependency-type: direct:production
...

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

Holmes/fuzzers/requirements.txt

@@ -1,5 +1,5 @@
 Twisted==14.0.0
 lxml==3.3.5
-psutil==2.1.1
+psutil==5.6.6
 pyasn1==0.1.7
 tlslite==0.4.6