Get rid of module javadoc examples

[stoyanK7]

The examples from each module Javadoc have to be removed. For example the following:

 * <p>
 * To configure the check so that it check name
 * but ignore {@code abstract} modifier:
 * </p>
 * <pre>
 * &lt;module name="AbstractClassName"&gt;
 *   &lt;property name="ignoreModifier" value="true"/&gt;
 * &lt;/module&gt;
 * </pre>
 * <p>Example:</p>
 * <pre>
 * class Example2 {
 *   abstract class AbstractFirst {}
 *   abstract class Second {} // violation 'must match pattern '\^Abstract\.\+\$''
 *   class AbstractThird {}
 *   class Fourth {}
 *   abstract class GeneratorFifth {} // violation 'must match pattern '\^Abstract\.\+\$''
 *   class GeneratorSixth {}
 * }
 * </pre>

An exclusion list from XdocJavadoc validation is created at #13357. This list should be removed and validation should be skipped for all modules once it's time to close this issue.

[nrmancuso]

@stoyanK7 please share some details on how we will handle this isssue

[romani]

@stoyanK7 will provide numerous PRs on this in summer to cover all not simple cases (non java Checks, filters, some java), so good practices will popup by themselves