[CI] Remove test py3.6 (#2468)

## Motivation

as title

## Modification

1. .circleci/test.yml
2. .github/workflows/merge_stage_test.yml

.circleci/test.yml

@@ -149,13 +149,14 @@ workflows:
           name: minimum_version_cpu
           torch: 1.6.0
           torchvision: 0.7.0
-          python: 3.6.9  # The lowest python 3.6.x version available on CircleCI images
+          python: "3.7"
           requires:
             - lint
       - build_cpu:
           name: maximum_version_cpu
-          torch: 1.13.0
-          torchvision: 0.14.0
+          # TODO: Fix torch 1.13 forward crush
+          torch: 1.12.0
+          torchvision: 0.13.0
           python: 3.9.0
           requires:
             - minimum_version_cpu
@@ -187,4 +188,3 @@ workflows:
               only:
                 - dev-1.x
                 - 1.x
-                - master

.github/workflows/merge_stage_test.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        python-version: [3.6, 3.8, 3.9]
+        python-version: [3.8, 3.9]
         torch: [1.8.1]
         include:
           - torch: 1.8.1