Update HealthCheckPublisherOptions.cs

This seems wrong.

Presumably fixes: https://github.com/aspnet/Extensions/issues/1041\n\nCommit migrated from b3c88d78fe

src/HealthChecks/HealthChecks/src/HealthCheckPublisherOptions.cs

@@ -60,7 +60,7 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
                     throw new ArgumentException($"The {nameof(Period)} must not be infinite.", nameof(value));
                 }
 
-                _delay = value;
+                _period = value;
             }
         }