Update min rust version to 1.40

Wu Yu Wei · Wu Yu Wei · commit 8ef116b2d0cd · 2022-04-28T17:22:44.000+08:00
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -16,7 +16,7 @@ jobs:
           - nightly
           - beta
           - stable
-          - 1.36.0
+          - 1.40.0
         features:
           -
           - --features dummy_match_byte
