CI: remove Go 1.16

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Author: AkihiroSuda

.github/workflows/main.yml

@@ -9,7 +9,7 @@ jobs:
   main:
     strategy:
       matrix:
-        go-version: [1.16.x, 1.17.x]
+        go-version: [1.17.x]
         platform: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.platform }}
     steps: