Fix user visible check (#21210)

Fixes #21206

If user and viewer are equal the method should return true.
Also the common organization check was wrong as `count` can never be
less then 0.

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

tests/integration/api_nodeinfo_test.go

@@ -32,7 +32,7 @@ func TestNodeinfo(t *testing.T) {
 		DecodeJSON(t, resp, &nodeinfo)
 		assert.True(t, nodeinfo.OpenRegistrations)
 		assert.Equal(t, "gitea", nodeinfo.Software.Name)
-		assert.Equal(t, 23, nodeinfo.Usage.Users.Total)
+		assert.Equal(t, 24, nodeinfo.Usage.Users.Total)
 		assert.Equal(t, 17, nodeinfo.Usage.LocalPosts)
 		assert.Equal(t, 2, nodeinfo.Usage.LocalComments)
 	})