Make javadoc <p> style guide compliant

This led to confusion for an open source contributor about how to format
code. We don't want to be like, "do as I say, not as I do."

https://google.github.io/styleguide/javaguide.html#s7.1.2-javadoc-paragraphs
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=122589700

java/google/registry/model/mark/MarkPhoneNumber.java

@@ -18,8 +18,8 @@ import google.registry.model.eppcommon.PhoneNumber;
 
 /**
  * Mark Holder/Owner Phone Number
- * <p>
- * This class is embedded inside {@link CommonMarkContactFields} hold the phone number of a mark
+ *
+ * <p>This class is embedded inside {@link CommonMarkContactFields} hold the phone number of a mark
  * contact or holder. The fields are all defined in parent class {@link PhoneNumber}, but the
  * subclass is still necessary to pick up the mark namespace.
  *