.github/workflows: drop windows/arm support

Author: hajimehoshi

.github/workflows/test.yml

@@ -54,7 +54,6 @@ jobs:
           # Check cross-compiling Windows binaries.
           env GOOS=windows GOARCH=386 go build -v ./...
           env GOOS=windows GOARCH=amd64 go build -v ./...
-          env GOOS=windows GOARCH=arm go build -v ./...
           env GOOS=windows GOARCH=arm64 go build -v ./...
 
           # Check cross-compiling macOS binaries.