Remove Dockerfile.solaris reference

Remove Dockerfile.solaris reference in `hack/make/.detect-daemon-osarch`
as `Dockerfile.solaris` has been removed.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

hack/make/.detect-daemon-osarch

@@ -60,9 +60,6 @@ case "$PACKAGE_ARCH" in
 			windows)
 				DOCKERFILE='Dockerfile.windows'
 				;;
-			solaris)
-				DOCKERFILE='Dockerfile.solaris'
-				;;
 		esac
 		;;
 	*)