Bump networkx version to 2.8.6

Author: mateusztabaka

tools/accuracy_checker/requirements.in

@@ -4,7 +4,7 @@ tqdm>=4.54.1
 # image reading and preprocessing
 # networkx version upperbound in scikit-image is conflicted
 networkx~=2.5;python_version<"3.7"
-networkx<2.8.1;python_version>="3.7"
+networkx>=2.8.6;python_version>="3.7"
 # note: python 3.6 wheels is not available since 0.18
 scikit-image~=0.17.2;python_version<"3.7"
 scikit-image>=0.19.2;python_version>="3.7"