[requires.io] dependency update (#1233)

Co-authored-by: requires.io <[email protected]>

tox.ini

@@ -12,9 +12,9 @@ python =
 passenv =
     GITHUB_*
 deps =
-    pytest==5.4.3
+    pytest==6.0.1
     pytest-cov==2.10.0
-    pytest-xdist==1.33.0
+    pytest-xdist==1.34.0
     hypothesis>=5.5,<6
 commands =
     pytest --cov-report=xml  --cov-report=term --cov=h2 {posargs}
@@ -42,15 +42,15 @@ commands =
 [testenv:graphs]
 basepython = python3.8
 deps =
-    graphviz==0.13.2
+    graphviz==0.14.1
 commands =
     python visualizer/visualize.py -i docs/source/_static
 
 [testenv:packaging]
 basepython = python3.8
 deps =
-    check-manifest==0.41
-    readme-renderer==25.0
+    check-manifest==0.42
+    readme-renderer==26.0
     twine==3.2.0
 commands =
     check-manifest
@@ -60,7 +60,7 @@ commands =
 [testenv:h2spec]
 basepython = python3.8
 deps =
-    twisted[tls]==19.10.0
+    twisted[tls]==20.3.0
 whitelist_externals = {toxinidir}/test/h2spectest.sh
 commands =
     {toxinidir}/test/h2spectest.sh