Revert addition of -compat=1.17 to (go mod tidy)

Typically, the compat with earlier versions causes us to use
newer versions of dependencies, which can only be a good thing.

Over time, the 1.17 version reference is just going to become obsolete.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Makefile

@@ -245,7 +245,7 @@ test-unit-local: bin/skopeo
 	$(GO) test $(MOD_VENDOR) -tags "$(BUILDTAGS)" $$($(GO) list $(MOD_VENDOR) -tags "$(BUILDTAGS)" -e ./... | grep -v '^github\.com/containers/skopeo/\(integration\|vendor/.*\)$$')
 
 vendor:
-	$(GO) mod tidy -compat=1.17
+	$(GO) mod tidy
 	$(GO) mod vendor
 	$(GO) mod verify