Add missing closing tag,
Add missing closing tag,

for xml doc of ToString of DomainName.

sean-gilliam/AutoFixture,AutoFixture/AutoFixture,hackle/AutoFixture,adamchester/AutoFixture,zvirja/AutoFixture,hackle/AutoFixture,sergeyshushlyapin/AutoFixture,adamchester/AutoFixture,sergeyshushlyapin/AutoFixture,Pvlerick/AutoFixture,dcastro/AutoFixture,sbrockway/AutoFixture,sbrockway/AutoFixture,dcastro/AutoFixture