Bump reportlab from 3.4.0 to 3.6.13

Bumps [reportlab](http://www.reportlab.com/) from 3.4.0 to 3.6.13.

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

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

requirements.txt

@@ -114,7 +114,7 @@ PyYAML==5.4
 rdflib==4.2.2
 readme-renderer==24.0
 regex==2020.5.13
-reportlab==3.4.0
+reportlab==3.6.13
 requests==2.22.0
 requests-toolbelt==0.9.1
 requests-unixsocket==0.1.5