Bump pyyaml from 3.13 to 5.1 in /benchmarks/scripts

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 3.13 to 5.1.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/master/CHANGES)
- [Commits](yaml/pyyaml@3.13...5.1)

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

benchmarks/scripts/requirements.txt

@@ -54,7 +54,7 @@ pyparsing==2.4.0
 python-dateutil==2.8.0
 pytz==2019.1
 PyVCF==0.6.8
-PyYAML==3.13
+PyYAML==5.1
 requests==2.21.0
 rsa==4.0
 scipy==1.2.2