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/ui/server/api/CheckApiServlet.java

@@ -57,8 +57,8 @@ import javax.servlet.http.HttpServletResponse;
 
 /**
  * A servlet that returns availability and premium checks as json.
- * <p>
- * This servlet returns plain JSON without a safety prefix, so it's vital that the output not be
+ *
+ * <p>This servlet returns plain JSON without a safety prefix, so it's vital that the output not be
  * user controlled, lest it open an XSS vector. Do not modify this to return the domain name in the
  * response.
  */