chore: Update go runtime in conformance tests (#182)

Author: dazuma

.github/workflows/conformance.yml

@@ -37,7 +37,7 @@ jobs:
     - name: Setup Go
       uses: actions/setup-go@fac708d6674e30b6ba41289acaab6d4b75aa0753 # v4.0.1
       with:
-        go-version: '1.17'
+        go-version: '1.21'
         check-latest: true
     - name: Setup Ruby
       uses: ruby/setup-ruby@8a45918450651f5e4784b6031db26f4b9f76b251 # v1.150.0