feat: drop darwin/i386 from README and Makefile

Author: shirou

Makefile

@@ -39,7 +39,6 @@ endif
 
 vet:
 	GOOS=darwin GOARCH=amd64 go vet ./...
-	GOOS=darwin GOARCH=386 go vet ./...
 	GOOS=darwin GOARCH=arm64 go vet ./...
 
 	GOOS=dragonfly GOARCH=amd64 go vet ./...

README.md

@@ -31,7 +31,7 @@ can be skipped.
 - FreeBSD i386/amd64/arm
 - Linux i386/amd64/arm(raspberry pi)
 - Windows i386/amd64/arm/arm64
-- Darwin i386/amd64
+- Darwin amd64/arm64
 - OpenBSD amd64 (Thank you @mpfz0r!)
 - Solaris amd64 (developed and tested on SmartOS/Illumos, Thank you
   @jen20!)