release: change tar name to match prior releases

In prior releases we were not using this variable and instead were
self-constructing a release tar file.
This was changed in 27d7c50
The change means the variable is being used now and is causing the
artifacts to be produced to have a different name which may break
download scripts.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

Makefile

@@ -74,7 +74,7 @@ endif
 WHALE = "🇩"
 ONI = "👹"
 
-RELEASE=containerd-$(VERSION:v%=%).${GOOS}-${GOARCH}
+RELEASE=containerd-$(VERSION:v%=%)-${GOOS}-${GOARCH}
 CRIRELEASE=cri-containerd-$(VERSION:v%=%)-${GOOS}-${GOARCH}
 CRICNIRELEASE=cri-containerd-cni-$(VERSION:v%=%)-${GOOS}-${GOARCH}